In the aftermath of its coup, Thailand’s military junta has attempted to tighten its grip on this teetering country by snuffing out potential opposition and detaining scores of key political figures, including the former prime minister.

Saturday morning, there was no official word about the whereabouts of Yingluck Shinawatra, who until two weeks ago was Thailand’s elected leader. The military had summoned Yingluck and more than 100 prominent politicians or faction leaders, threatening them with arrest if they failed to show up. It also banned those leaders from leaving the country.

Some Thai media reported that Yingluck was being held at an army base north of Bangkok. Reuters quoted a senior military officer saying that Yingluck would be let go within a week.

“We just need to organize matters in the country first,” the officer said.

Yingluck’s detention was the most forceful move on a day when the Thai military appeared to have gained the cooperation of the bureaucrats in charge of running the country. There were scattered protests in Bangkok, and soldiers forcibly dispersed activist groups who said they opposed the coup.

Even as foreign governments from Washington to Tokyo urged Thailand to reestablish civilian rule, Thailand’s army chief, Gen. Prayuth Chan-ocha, gave no indication how long the military intends to maintain power.

Prayuth has set out a vague agenda calling for reforms and stability, goals that have evaded Thailand for decades. His initial moves, some Thais said, raised the specter of a prolonged junta leadership in one of Southeast Asia’s most critical but vulnerable democracies.

In its attempt to establish order, Thailand’s military has used aggressive measures. So far, there has been no explanation for the detention of more than 100 political leaders, who come from both sides of Thailand’s sparring factions. At least some have been held incommunicado, stripped of their mobile phones.

A small handful of political figures who’d been detained Thursday were released on Friday.

In Washington, State Department spokeswoman Marie Harf told reporters Friday that the United States had suspended about $3.5 million of its $10.5 million in annual aid to Thailand and is considering additional suspensions. The $3.5 million in suspended aid is from the Foreign Military Financing and International Military Education and Training programs, Harf said.

“We’ve consistently been in contact with military leaders throughout this period of political uncertainty,” she said. “We urge the immediate restoration of civilian rule, a return to democracy and obviously respect for human rights.”

The State Department also issued a travel alert recommending that U.S. citizens reconsider any “non-essential” travel to Thailand, particularly Bangkok.

Internally, the coup runs the risk of exacerbating Thailand’s long-standing political divisions, leading to violence or, in a worst-case scenario, civil war. But in the short term, the junta also faces another problem: legitimacy.
Prayuth on Friday afternoon invited diplomats to a meeting at which he tried to explain the coup, Thailand’s second in eight years.

“Prayuth’s highest priority is to secure his legitimacy,” said Sean Boonpracong, a national security adviser in Yingluck’s ousted administration.

If Prayuth is to gain legitimacy domestically, he needs the blessing of the country’s beloved king — a move that could come in the next few days, said Dej-udom Krairit, a senator who said he supports the coup. Dej-udom said he expects the military to remain in power for at least a year before handing the reins to a civilian government.

For years, Thailand has been riven by a dispute between a large bloc of rural voters and a smaller, urban group of traditional power holders. The rural class has been galvanized by Thaksin Shinawatra, a telecom tycoon who lives in self-imposed exile in Dubai but still commands a powerful political network that includes his younger sister, Yingluck.

Yingluck was elected in 2011 and had governed until earlier this month, when the Constitutional Court issued an abuse-of-power ruling that forced her to step down. Thailand’s courts are seen by some analysts as playing a partisan role, generally in opposition to Thaksin and his relatives.

Thailand’s military has occasionally used tensions between Thaksin and his opponents as an excuse to intervene. On Friday, there were only a few signs of defiance, with some activists and small groups in Bangkok publicly declaring opposition to the coup. The military has issued a broad edict banning such dissent — a rule that also applies to social media.

The military’s bold actions suggested that Prayuth is taking a hard line, some analysts said.

On the one hand, said political analyst Thitinan Pongsudhirak, the general is following a “coup template” — maintaining law and order and setting up an interim government. But on the other hand, initial indications are that the “interim coup period will be much more repressive,” he said.

A retired U.S. diplomat in Thailand, speaking on the condition of anonymity, called the military’s actions sweeping compared with what happened in some previous coups, including the last one in 2006 that toppled Thaksin . “Other developments over the next year could be a game-changer in the struggle for Thailand,” the diplomat said in an interview.

Prayuth, 60, was expected to retire in October. He has now been quoted as saying that if the strife is not resolved before his scheduled departure from military service, he will stay on.

“That’s bad news not just for the next guy in line, but also for Thailand,” said the former U.S. diplomat.

Domestic and international television networks returned to the air Friday. But the military asked social-media operators to cooperate in stopping messages that “incite violence, break the law or criticize the coup council.”

Social-media networks Twitter, Facebook and others remained accessible.

On the streets of Bangkok, vendors still cluttered the sidewalks and cars clogged the streets, and there was little noticeable military presence. But normalcy disappeared in the evening as Thais rushed home to beat a 10 p.m. curfew instituted Thursday.

During business hours, Thais drove, biked, taxied and took public transport to work, unfazed by the change from democracy to military autocracy.

Locals and foreigners alike were out and about, many seemingly oblivious to the coup — a comfort zone boosted by the almost complete absence of soldiers on the streets. A trio of camouflage-garbed soldiers loitered and rode a motorcycle near the major Ratchaprasong intersection, but appeared uninterested in civilians, other than allowing them to snap a few photos.

Lennox Samuels in Bangkok and William Branigin in Washington contributed to this report.