The Thai military launched a coup d'etat against Prime Minister Thaksin Shinawatra late last night while he is in New York to attend the United Nations General Assembly.

Coup leaders said they have revoked the constitution, imposed martial law and appointed a new prime minister as tanks rolled into the streets of Bangkok.

An announcement made on both television and radio stations declared that the 'Council of Administrative Reform' had seized power in the capital without a shot being fired.

Coup spokesman Retired Lieutenant-General Prapart Sakuntanak said the seizure would be temporary and power "returned to the people" soon.

Prapart added that a body would be set up to decide on political reforms.

"Never in Thai history have the people been so divided," Prapart was quoted by Reuters as saying.

"The majority of people had become suspicious of this administration, which is running the country through rampant corruption," he added.

"Independent bodies have been interfered with so much they could not perform in line within the spirit of the constitution."

Attempt to stave off coup failed

Earlier last night, Thaksin had tried to stave off the coup by declaring a state of emergency at about 10.20pm (11.20pm Malaysian time).

He spoke by audio on the local state-owned Channel 9 TV station from New York where he is attending the United Nations General Assembly.

However, the transmission was abruptly cut after 10 minutes while he was still talking.

Other local television channels have also stopped the usual programmes and air showed documentaries on the Thai royal family - an indication that the military has taken control over the stations.

The coup came on the eve of an anti-Thaksin demonstration planned for today in Bangkok - the first in six months - to demand the billionaire telecoms tycoon's resignation for alleged corruption and abuse of power.

There have been rumours of a military coup in the capital in the past few weeks but the military had repeatedly denied this.

The rumours picked up steam after an army lieutenant was arrested following the discovery of a powerful bomb in the trunk of a car parked near Thaksin's house on Aug 24.

There were also reports of several military units being moved from Bangkok to the restive southern provinces.

According to The Nation daily's website, soldiers loyal to Army Commander-in-Chief Sonti Boonyaratrin have staged a coup - the first in 15 years - after negotiations with the government failed.

The news came minutes after Thaksin declared a state of emergency and ordered all troops to remain in their barracks. But it appeared the military has ignored his orders.

About 50 soldiers, accompanied by two tanks, were seen taking over the Government House where the prime minister's office is located.

Reporters who were at the Government House were told to leave the area. Tanks and soldiers were also seen on many street corners although Bangkok remained quiet.

Ministers arrested

There were reports that the military has arrested two key ministers, Deputy Prime Minister Chidchai Wannasathit and Defense Minister Thammarak Isaragura na Ayuthaya - both key loyalists of Thaksin.

Sonthi ( left ), the first Muslim army chief, has been in loggerheads with Thaksin over the annual military reshuffle, with the premier trying to put his own people in the top posts.

The army commander-in-chief is considered the most powerful position in the Thai military hierarchy. Most of the 17 previous coups over the past 60 years in Thailand had been staged by the army chief.

Sonthi, 59, who was appointed to the army's top post last year by Thaksin with a mission to deal with an Islamic insurgency in the country's south, said he will temporarily be assuming the duties of prime minister.

Thaksin is currently in New York to deliver a speech at the UN General Assembly. He has initially moved forward his speech to Tuesday night but later cancelled his speech.

He is believed to be holed up at a hotel in Manhattan, just a few blocks from the UN headquarters.

A foreign ministry official, who spoke on condition of anonymity, said Thaksin still tentatively planned to fly back to Thailand today.

However, political observers in Bangkok said that the prime minister could be either detained or arrested on arrival.

Thaksin has faced massive street protests demanding his ouster since late last year after his family sold a stake in its telecommunications business for US$1.9 billion (RM7 billion) without paying taxes. The protests resulted in a political crisis that has dragged on for months.

He called a snap election in April 2 which he won, but it was declared invalid by the court. Another election was to be held later in the year.