Troops detained at least two activists during the protest in downtown Bangkok, which descended into scuffles but ended without injury and marked one of the first open challenges to the military since Thursday's coup.
The junta, though, remained firmly in charge, summoning more than 100 top political figures — the entire ousted government, their associates and a handful of their opponents. It also banned those on its wanted list from leaving the country.
Among the officials who showed up at an army compound in Bangkok were former Prime Minister Yingluck Shinawatra, sacked earlier this month for nepotism by the Constitutional Court, and her temporary replacement Niwattumrong Boonsongpaisan, according to Yingluck's aide Wim Rungwattanachinda.
After about 30 minutes, Yingluck left the facility and was taken to another army location by soldiers, said Wim, who added that it appeared she would not be immediately released.
It was unclear what the military's intentions were beyond the summons, which it said had been issued "to keep peace and order and solve the country's problems."
By nightfall, dozens of the VIPs who turned themselves in were still being held, although at least eight ex-Cabinet ministers had been released.
Education Minister Chaturon Chaisang, an outspoken critic of the military's intervention in politics, remained in hiding. Chaturon said in a Facebook post that the coup would only worsen the country's political atmosphere. He vowed not to turn himself in, but said he would not resist arrest.
Most of the country was calm, and there was little military presence on Bangkok's streets. Although life had largely returned to normal during the day, an overnight curfew from 10 p.m. to 5 a.m. was still in effect.
Restrictions on TV broadcasts and on posting inflammatory comments on social media remained in effect, and many Thais were reluctant to comment publicly on the coup.
There were no reports of any major unrest, including in the former government's political strongholds in the north. In the northeast city of Chiang Mai, about 100 anti-coup demonstrators took to the streets, but no violence was reported and the protesters dispersed on their own.
The army staged the coup Thursday just after a military-hosted meeting of political rivals to resolve the country's political deadlock.
After two hours and no resolution, armed soldiers detained the participants, including four Cabinet ministers, and army chief Gen. Prayuth Chan-ocha appeared on national television to announce the takeover. Hours later, the junta suspended the constitution and banned gatherings of more than five people.
Prayuth defended the coup as necessary to restore stability amid increasing spasms of violence that together with controversial court rulings had rendered the government powerless.
He briefed foreign diplomats Friday about the coup and said the lifespan of the ruling military council would depend on how soon the current political conflict can be eased, Foreign Ministry Permanent Secretary Sihasak Phuangketkeow said.
He said Prayuth told them a reform council would be established along with an interim government, and that they would lead to an eventual election.
Fears remain, however, that the coup will only result in more violence and deepen the nation's crisis.
Thursday's dramatic events were the latest response to a societal schism laid bare after the 2006 coup deposed former Prime Minister Thaksin Shinawatra, the older brother of Yingluck and a billionaire tycoon whose populist movement has won every national election since 2001. Thaksin lives in self-imposed exile to avoid corruption charges, but he still wields enormous influence over Thailand's political affairs and remains at the heart of the ongoing crisis.
It is a divide that has led to upheaval multiple times in recent years. The latest crisis alone has left 28 people dead and more than 800 wounded since November.
U.S. Secretary of State John Kerry condemned the takeover and warned it would have a negative impact on U.S.-Thai relations. The State Department said it has suspended $3.5 million in military aid and is reviewing a further $7 million in bilateral assistance and other aid.
British Foreign Secretary William Hague said his country looked to Thai authorities "to set out a quick clear timetable for elections to help re-establish the democratic framework of governance.
"There should never be recourse to violence: only by openly discussing the full range of issues can Thailand move forward and reach a more stable position," he said in a statement.
Associated Press writers Todd Pitman and Jocelyn Gecker and video journalists Raul Gallego and Chalida Ekvitthayavechnukul in Bangkok, and AP writer Matthew Pennington in Washington contributed to this report.
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