Updated

The Pentagon on Saturday canceled military exercises in Thailand amid a military coup and urged organizers to restore democracy in the Southeast Asian country.

The Pentagon canceled three upcoming events with the Royal Thai Armed Forces and suggested U.S. military aid could be stopped and U.S. military relations with Thailand would remain fractured until junta leaders restore democracy “including a clear path forward to elections.”

“While we have enjoyed a long and productive military-to-military relationship with Thailand, our own democratic principles and U.S. law require us to reconsider U.S. military assistance and engagements,” said Pentagon press secretary Rear Adm. John Kirby.

On the same day, the new army junta ordered dozens of outspoken activists, academics and journalists to surrender themselves to military authorities, a move apparently aimed at neutralizing critics and potential opposition.

The junta, which is already holding most of the government it ousted in a coup Thursday in secret locations against their will, said it would keep former Prime Minister Shinawatra and others in custody for up to a week to give them "time to think" and keep the country calm.

Two days after the army seized power in the nation's first coup in eight years, it also faced scattered protests that came amid growing concern over the junta's intentions. Also Saturday, the military dissolved the Senate -- the last functioning democratic institution left, and absorbed its legislative powers.

The three canceled events are the ongoing Exercise Cooperation Afloat Readiness and Training 2014, a visit in June to Thailand by U.S. Pacific Fleet Commander Adm. Harry Harris and an invited visit next month to the U.S. Pacific Command for Royal Thai Armed Forces Commander General Tanasak Patimapragorn.

There were 700 U.S. troops participating in the annual naval exercises, which include sailors, marines, ships and aircraft.

“We urge the Royal Thai Armed Forces to act in the best interests of their fellow citizens by ending this coup and restoring the rule of law and the freedoms assured those citizens through democratic principles," Kirby also said.

At least 100 people, mostly top politicians, have been detained incommunicado so far. Deputy army spokesman Col. Weerachon Sukondhapatipak said they were all being well-treated and the military's aim was to achieve a political compromise.

Weerachon said all those held have had their cellphones confiscated because "we don't want them communicating with other people. We want them to be themselves and think on their own."

In a military order broadcast at the start of the day, the junta summoned 35 more people, including politicians, political activists and, for the first time, outspoken academics and some journalists.

One of those on the list, Kyoto University professor of Southeast Asian studies Pavin Chachavalpongpun, said by telephone from Japan that he would not turn himself in. He said the summons meant the junta felt insecure.

"The military claiming to be a mediator in the Thai conflict, that is all just nonsense," said Pavin, who is frequently quoted by foreign media as an analyst. "This is not about paving the way for reform and democratization. We are really going back to the crudest form of authoritarianism."

Beyond the U.S., multiple nations also have condemned the coup.

The Associated Press contributed to this report.