Prayuth made the announcement in a television broadcast after a meeting to which he had summoned the rival factions in Thailand's drawn-out political conflict, apparently with the aim of finding a solution to six months of anti-government protests.
"In order for the situation to return to normal quickly and for society to love and be at peace again ... and to reform the political, economic and social structure, the military needs to take control of power," Prayuth said.
Soldiers block the access to the Army Club where Thailand's army chief held a meeting with all rival factions during a coup in central Bangkok. (Reuters Photo)
Thailand's coup leaders ordered members of the now-deposed government's cabinet to report to the military by the end of the day. "In order to keep peace and order, the National Peace and Order Maintaining Council orders these persons to report themselves to the Council by May 22," said a statement read out on television by the military.
The military later declared a 10pm until 5am curfew. The military ordered protesters on both sides of the kingdom's political divide to disperse and go home after it seized power in a coup.
"In order to keep peace and order all protesters from every group must leave for their homes immediately," an army spokesman said in a televised address, adding that buses had been arranged to take them away.
The military also ordered all television and radio stations to suspend their usual programmes and show only the army's broadcasts in the wake of a coup. The move was to ensure the release of "accurate news to the people," an army spokesman said in a televised announcement.
Armed Thai soldiers take their positions inside an encampment of pro-government "red shirt" supporters in Nakhon Pathom province on the outskirts of Bangkok. Thailand's army chief General Prayuth Chan-ocha took control of the government in the coup saying the army had to restore order and push through reforms, two days after he declared martial law.(Reuters Photo)
Thailand is locked in a protracted power struggle between supporters of ousted former premier Thaksin Shinawatra and opponents backed by the royalist establishment that has polarised the country and battered its economy.
The Thai army has a long history of intervening in politics - there have been 18 previous successful or attempted coups since the country became a constitutional monarchy in 1932, most recently when Thaksin was deposed in 2006.
Hundreds of soldiers surrounded the meeting at Bangkok's Army Club shortly before the coup announcement and troops took away Suthep Thaugsuban, leader of the protests against the pro-Thaksin government.
Some of the other meeting participants were being held back in the venue afterwards, said a Reuters reporter waiting outside.
The army ordered rival protest camps to break up and soldiers fired into the air to disperse thousands of pro-government "red shirt" activists gathered in Bangkok's western outskirts, a spokesman for the group said.
The military detained at least one leader of the activists, said the spokesman, Thanawut Wichaidit.
A Reuters witness later said the protesters were leaving peacefully. Earlier, their leader, Jatuporn Prompan, said they would continue their rally despite the coup and the order to disperse.
The army had declared martial law on Tuesday, saying the move was necessary to prevent violence, but it rejected accusations its actions amounted to a coup.
Call for compromise
In a first round of talks on Wednesday, Prayuth had called on the two sides to agree on a compromise that would have hinged around the appointment of an interim prime minister, political reforms and the timing of an election.
Wednesday's talks ended inconclusively with neither side backing down from their entrenched positions, participants said.
The army has also clamped down on the media, including partisan television channels, and warned people not to spread inflammatory material on social media.
Leaders of the ruling Puea Thai Party and the opposition Democrat Party, the Senate leader and the five-member Election Commission had joined the second round of talks on Thursday.
Acting Prime Minister Niwatthamrong Boonsongphaisan, who did not attend, told reporters before the talks that his government could not resign as its enemies were demanding as that would contravene the constitution.
"The government wants the problem solved in a democratic way which includes a government that comes from elections," he said.
Government officials were not available for comment after the coup announcement.
Former telecommunications tycoon Thaksin has lived in self-exile since 2008 to avoid a jail term for graft, but still commands the loyalty of legions of rural and urban poor and exerts a huge influence over politics, most recently through a government run by his sister, Yingluck Shinawatra.
Yingluck was forced to step down as premier by a court two weeks ago, but her caretaker government, buffeted by six months of protests against it, had remained nominally in power despite the declaration of martial law this week.
Thailand's gross domestic product contracted 2.1 percent in January-March from the previous three months, largely because of the unrest, adding to fears it is stumbling into recession.
The protesters want to rid the country of the influence of Thaksin, who they say is a corrupt crony capitalist who commandeered Thailand's fragile democracy and used taxpayers' money to buy votes with populist giveaways.
They wanted a "neutral" interim prime minister to oversee electoral reforms before any new vote.
The government and its supporters said a general election that it would likely win was the best way forward and it had proposed polls on Aug. 3, to be followed by reforms.
Earlier on Thursday, anti-government protest leader Suthep, a former deputy prime minister in a government run by the pro-establishment Democrat Party, told his supporters victory was imminent.
Twenty-eight people have been killed and 700 injured since this latest chapter in the power struggle between Thaksin and the royalist elite flared up late last year.