WITH TWO people dead and more than 400 wounded in anti-government protests last week, cinemas in Thailand's capital have chosen a bad time to show Nicholas Cage's latest action movie - although its name, emblazoned on billboards across this anxious city, might seem grimly prophetic: Bangkok Dangerous.

Last Tuesday's protests by the People's Alliance for Democracy (PAD) have deepened months of political deadlock in Thailand and shattered confidence in the government of Somchai Wongsawat, who took office as prime minister only a month ago.

Somchai's predecessor was forced to resign amid protests by the PAD, an ultra-royalist group who want a radical reform of Thai politics. Their love of the nation's revered King Bhumibol Adulyadej is matched by their loathing of the former prime minister, Thaksin Shinawatra, who was toppled in a 2006 military coup and is now seeking political asylum in the UK.

Rumour of another coup swirled in the aftermath of last Tuesday's running battles in Bangkok's historic heart. It began soon after dawn when riot police, apparently without warning, fired tear-gas at PAD protesters who had sealed off roads around the Thai parliament, where Somchai was scheduled to read a policy statement. Many people were injured and a photograph published on the front page of many Thai newspapers showed a protester with his lower leg blown off. The street battles went on late into the evening.

Parliament was convened and Somchai hastily read his statement. The session ended when PAD members reportedly cut power to the building, plunging it into darkness. Thousands of protesters then occupied the surrounding streets, trapping Somchai and other politicians inside.

The PM was forced to make a humiliating exit by climbing over a fence into Vimanmek Mansion, a teak palace popular with foreign tourists, then fleeing the area in an awaiting helicopter.

Soon afterwards, I watched a battle erupt at an intersection northwest of the parliament, as hundreds of riot police tried to break through PAD barricades to rescue MPs remaining inside. Police fired dozens of tear gas canisters, but protesters - many wearing motorcycle helmets and swimming goggles for protection - doused the gas clouds with bottles of water. Then they fought back with rocks, slingshots and, claim some witnesses, guns.

Ambulances raced into the area, then raced out again when one was apparently struck by a tear-gas canister. I saw three people with minor injuries stretchered from the area. But worse was to come.

Amid the chaos, a suspected car bomb went off in a nearby street, killing protester Methee Chartmontri, a former police officer and brother-in-law of a PAD leader. Emergency workers approached the burnt-out wreck to lay a sheet over a human torso which had been shorn of limbs by the blast.

It took police more than an hour to create a path to parliament, finally allowing the politicians to leave by bus. But the PAD - who count many former policemen and soldiers among their ranks - are well-drilled and not easily frightened, and battles continued to rage across the area. One claimed the life of university student Angkhana Radappanyawut, 28, who died from chest injuries on the way to hospital.

Just before sunset, protesters with petrol bombs charged another intersection near the parliament, forcing police to retreat behind a road littered with vandalised police vans and buses. I arrived there to hear what sounded like gunfire - a Japanese photographer later claimed it came from the PAD.

The police retreated, and the noise of exploding canisters was replaced by the screeches of panicked monkeys in a nearby zoo. After further confrontations to the south, including one outside the Metropolitan Police Headquarters, dozens of ambulances raced into the area to take away the wounded.

By 7pm, the arrival of a dozen trucks of soldiers, all seemingly unarmed, was cheered by the crowds. The troops helped police restore a fragile calm, although their presence sparked rumours that another military coup was underway. Army chief General Anupong Paojinda denied this, saying: "The army will not take sides."

Somchai, who visited injured protesters and police in hospital, rejected calls to resign, vowing he would resolve the crisis by democratic means.

But the violence has disgusted millions of ordinary Thais and polarised the political scene. "All these people are here for one reason: they love the country, they love His Majesty the King," said Anusart Suwanmongkol, an appointed senator, while visiting protesters. He called the police action "silly and tragic".

Following the protests, a pilot with Thai International Airways was suspended for refusing to allow three pro-government politicians on board his plane, while some doctors at an elite Bangkok hospital said they would not treat injured police.

The police claim they fired only tear gas, but the seriousness of many injuries has caused the PAD and other government critics to dispute this. Four people required amputations, while four others lost fingers and toes, Thai media reported. The injuries were caused by "lethal ammunition brought to the demonstration by the protesters themselves," insisted a police spokesman.

Doctors who examined Angkhana Radappanyawut's body questioned whether a gas canister caused the student's fatal injuries. Police suggested she was killed by a bomb carried under her arm or in her bag. A PAD website claimed she was "killed by a grenade shot directly at her chest".

The truth is probably less sinister, suggested one Thai forensics expert. Poorly trained police were using Chinese-made tear-gas canisters which are fired at high speed and, unlike other types which slowly release gas, explode with enough force to cause horrific injuries. At the blood-stained site of the morning clash, I saw army medics searching for body parts beneath abandoned cars.

Some 20 policemen were also injured. Four were shot by the PAD, claimed deputy Metropolitan Police chief Pol Maj-Gen Amnuay Nimmano. One officer was stabbed with a sharpened flag pole, and another suffered broken legs after a PAD member ran him over with an SUV.

The PAD is primarily made up of urban, middle-class Thais who are agitating for radical reforms to prevent corrupt politicians taking power by buying rural votes. Its urban membership is at odds with country folk in Thailand's north and northeast, where Thaksin's populist policies while in power won him lasting popularity.

Two prominent PAD leaders are Sondhi Limthongkul, a media firebrand who broadcasts PAD speeches via his own television station, and Chamlong Srimuang, a wily former general who has helped the PAD repeatedly outmanoeuvre the police. The group is well-funded and prepared to use unconventional tactics - last Tuesday, sewage trucks emptied the mobile latrines parked at protest sites, then sprayed the contents on roads where riot police might advance.

PAD protests formed the backdrop to both the army's seizure of power from Thaksin in September 2006 and the resignation last month of his successor, Samak Sundaravej, whom the PAD regarded as Thaksin's proxy.

Thousands of its members besieged the British Embassy in Bangkok in August to demand that the British government deny asylum to Thaksin and his wife, Pojaman. Days later, the PAD overran the Thai prime minister's office, known as Government House, raided a national broadcaster, and blockaded Phuket airport. In a previous clash with pro-government protesters, PAD members beat a man to death, while foreign journalists claimed to have heard gunfire from their ranks.

Today, thousands of PAD protesters are still camped out on the lawns of Government House and in nearby streets. Visitors must pass through razor-wire barricades and undergo bag and ID checks by black-clad PAD guards, who wear magical charms they believe render them invulnerable. The protesters are armed with clubs, slingshots and - betraying the group's middle-class origins - golf clubs.

Somchai, who must now hold his Cabinet meetings in a converted VIP lounge at Bangkok's old airport, is an obvious PAD hate-figure: he is also Thaksin's brother-in-law. Yet before last Tuesday's violence it was still hoped that the soft-spoken former judge might fashion a compromise with the PAD and end the political deadlock.

The PAD-initiated violence in August lost the group support in many sections of Thai society. Viewed cynically, the deaths of two of their members last week has invigorated the group's flagging momentum. The protesters provoked the violence, knowing that the subsequent crackdown would be a "lose-lose proposition" for the government, believes Dr Thitinan Pongsudhirak, a political scientist at Bangkok's Chulalongkorn University. "Now the PAD are exploiting this to recruit a lot of foot soldiers," he says.

The PAD has played a role in toppling two recent Thai leaders. Will Somchai be the third? "His days are numbered," says Pongsudhirak. The Cabinet has set up committees to investigate the police action and compensate victims. But the PAD remains defiant. "We will continue to fight in a peaceful way to topple the killer government," Somsak Kosaisuk, one of its leaders, told reporters.

The PAD received a boost on Thursday, when a Bangkok appeals court dropped charges of insurrection against nine of its leaders, filed by police after the group's August takeover of the prime minister's office.

Anupong has predicted further unrest, while a deputy prime minister, who resigned after last week's violence, has publicly called for a military coup to solve the political deadlock. Pongsudhirak describes as "very credible" reports that senior officers are privately pressuring Anupong to do the same.

An editorial in Friday's Bangkok Post speculated that the precipitating a military coup "could very likely be the aim of the PAD leaders," by toppling another elected government and ushering in their overhaul of the political system.

But another coup - Thailand has had 18 of them in modern times - could conceivably benefit PAD's arch-enemy Thaksin, by bolstering his case for political asylum in the UK. With the global economy in turmoil, all this is as ill-timed as the release of Bangkok Dangerous - last week the Thai stock exchange fell to a five-year low and trading was briefly halted on Friday after the index plunged 10%.

The UK Foreign Office is currently advising travellers to Thailand to "exercise caution, avoiding any demonstrations or large gatherings of people" and warned: "There remains the possibility of further violent clashes."

Pongsudhirak agrees: "The PAD are like a bulldozer. They will keep pressing on and try to broaden their base through intimidation and fear."