Thai PM 'overthrown in army coup'
Military leaders in Thailand say they have overthrown the country's Prime Minister, Thaksin Shinawatra.
Soldiers seized government offices and took up strategic positions around the capital, Bangkok. Parliament and the constitution have been suspended.
The head of the army, Gen Sonthi Boonyaratglin, will act as acting prime minister, an army spokesman said.
But a spokesman for Mr Thaksin, who is at the UN in New York, insisted the government was still in control.
The spokesman said the coup "could not succeed". It had not been decided when the prime minister would return home from the UN, he added.
However, in a broadcast on all Thai television channels, the leadership of the armed forces said it had taken control of Bangkok, declared nationwide martial law and ordered all troops to return to their bases.
"We ask for the co-operation of the public and ask your pardon for the inconvenience," the announcement said.
Declaring themselves the "Council of Political Reform", the rebels said they were led by Gen Sonthi, visited the king and declared loyalty to him.
However, the BBC's Kate McGeown in Bangkok says the declaration of loyalty to King Bhumibol - held in high esteem by most Thais - does not necessarily imply that he backs the takeover attempt.
Our correspondent says low-level rumours of a possible coup have been circulating for weeks.
There has been pressure growing on the prime minister to resign, including from groups close to King Bhumibol, following a political impasse in which April's general election was declared invalid.
Witnesses said several hundred troops were posted at key points around Bangkok, including at government installations and major intersections.
The streets in Bangkok were quiet on Tuesday night, our correspondent in the city says. People were calm for the most part, curious about what was going on, but some said they were scared.
Traffic moved through the streets normally and in the bars of the city centre, foreign tourists seemed oblivious to what was going on.
One soldier on a tank said: "We don't know why we're here, we've been told to say nothing. We're just following orders."
Russell Miles emailed the BBC News website to say there were troops "dressed in Swat-style gear strolling around" near Government House, and "a tense, but fairly controlled atmosphere".
He said: "We saw a group of blokes bundling a cameraman and another chap into a van. We are taking photos, but not out in the open."
The military said the country's stock market, banks and schools would remain closed on Wednesday.
BBC World, CNN and other international news channels were taken off the air, and Thai stations played out images of the royal family and patriotic songs.
The EU's Finnish presidency expressed "grave concern" at events, and the US called on Thais "to resolve their political differences in a peaceful manner".
It is the first coup attempt in 15 years in a country where they used to be commonplace.
At the United Nations, where the annual General Assembly is under way, it was announced that the Mr Thaksin's address had been cancelled.