Ousted Thai Prime Minister Yingluck Shinawatra and dozens of other political figures have disappeared since arriving for meetings with military leaders who took power in a coup this week, and reports indicate the prime minister has been detained.
After being summoned by the army, Yingluck and others arrived at a military installation in Bangkok Friday.
The country's caretaker prime minister, Niwattumrong Boosongpaisan, was among other officials summoned by the military. Until the coup, he had been in charge of the kingdom on an acting basis, after a court ordered Yingluck to step down.
Quoting a senior Thai military officer, Reuters news agency reported Yingluck is being detained "for up to one week."
The military already had banned her and more than 150 other political figures from leaving Thailand without permission.
Broadcasters in Thailand began resuming normal operations late Friday.
The coup on Thursday was bloodless - without violence - although military leaders also ordered a nighttime curfew nationwide and suspended the constitution.
Gen. Prayuth Chan-Ocha said coup leaders aim to restore public order and push through political reforms. Thailand has been wracked by six months of political disputes and sometimes violent demonstrations.
U.S. Ambassador to Thailand Kristie Kenney told VOA's Steve Herman on Friday that Washington is concerned about the human-rights situation. Initial reactions to the upheaval in Bangkok from the United States and other Western governments have called for a quick return to civilian rule and criticized the military intervention as unnecessary.
"The Thais will of course chart their own path. But as Secretary of State [John] Kerry has said, we really do call for an immediate return to a civilian government, the lifting of press restrictions, and respect for human rights and a path to elections," Kenney said.
Yingluck is the sister of Thaksin Shinawatra, a billionaire telecommunications tycoon turned politician who won huge support among the poor but the loathing of the royalist establishment, largely over accusations of corruption and nepotism. He was removed as premier in another military coup in 2006.
Thursday's coup followed a declaration of martial law and the end of crisis talks between rival political parties. Witnesses said the participants in the talks were led away by soldiers after they failed to agree on a compromise between the opposition and supporters of ex-Prime Minister Thaksin Shinawatra, Ms. Yingluck's brother. Most are still believed to be in detention.
Thailand's political crisis reached a breaking point earlier this month when Yingluck and several Cabinet members were ousted by the Supreme Court for abuse of power. But the opposition continued its protests, demanding the entire government step aside. Nearly 30 people have been killed during six months of anti-government protests.
Thailand's army has staged 12 coups in the last 80 years.