Australia used stronger language, saying it was concerned to see democracy "destroyed."

"We deeply regret the fact that such a coup has taken place; obviously to see democracy destroyed in that way is a matter for grave concern to us," Foreign Minister Alexander Downer told Australian Broadcasting Corp. radio by telephone from New York.

Thaksin recently alienated a segment of the military by claiming senior officers had tried to assassinate him in a failed bombing attempt. He also attempted to remove officers loyal to Sondhi from key positions.

Sondhi, who is known to be close to Thailand's revered constitutional monarch, will serve as acting prime minister, army spokesman Col. Akarat Chitroj said. Sondhi, well-regarded within the military, is a Muslim in this Buddhist-dominated nation.

Sondhi, 59, was selected last year to head the army partly because it was felt he could better deal with the Muslim insurgency in southern Thailand, where 1,700 people have been killed since 2004. Recently, Sondhi urged negotiations with the separatists in contrast to Thaksin's hard-fisted approach. Many analysts have said that with Thaksin in power, peace in the south was unlikely.

In New York, Thaksin declared a state of emergency in an audio statement via a government-owned TV station in Bangkok — a vain attempt to stave off the coup. He later canceled a scheduled address to the U.N. General Assembly.

A Foreign Ministry official, who spoke on condition of anonymity because he was not authorized to speak to the media, said Thaksin tentatively planned to return to Thailand quickly. The official said he could not comment on the possibility of his being arrested if he returned.

Government spokesman Surapong Suebwonglee, who was with Thaksin, said the coup leaders "cannot succeed" and was confident they would fail "because democracy in Thailand has developed to some ... measure of maturity."

However, Sondhi's troops appeared to be in full control and clearly enjoyed the support of the monarch.

Former Prime Minister Chuan Leekpai, a member of the opposition Democrat Party, reflected an ambivalence that is likely to surface in coming days.

"As politicians, we do not support any kind of coup, but during the past five years the government of Thaksin created several conditions that forced the military to stage the coup. Thaksin has caused the crisis in the country," he told The Associated Press.

Thaksin, a telecommunications tycoon turned politician, handily won three general elections since coming to power in 2001 and garnered great support among the rural poor for his populist policies.