Thailand's army has declared martial law across the country to restore order following months of anti-government protests that have left 28 people dead and hundreds wounded.
An announcement on military-run television on Tuesday said martial law had been invoked "to restore peace and order for people from all sides", stressing that the move "is not a coup".
"The public do not need to panic but can still live their lives as normal," it added.
A proposed political amnesty bill sparked mass protests late 2013. Critics feared it would allow ousted PM Thaksin Shinawatra, convicted of corruption, to return.
His sister Yingluck, then PM, called early elections. The Constitutional Court declared results invalid due to opposition disruption.
On May 7, the Constitutional Court ruled that Yingluck had to step down for abuse of power. Parts of her government stayed on in a caretaker capacity.
The move gave the military control of nationwide security.
Chaikasem Nitisiri, the justice minister, told the Associated Press news agency that the army had not consulted the cabinet.
He played down the move, saying the caretaker government was still running the country but that the army was now in charge of security.
"Security matters will be handled solely by the military, and whether the situation intensifies or is resolved is up to them," he said.
Al Jazeera's Scott Heidler, reporting from Bangkok, said the measure was taken to prevent more flare-ups of violence between rival protesters.
He said soldiers had been deployed to areas where there were anti- or pro-government protesters and that the army had been given the authority to break up gatherings of more than five people, although it did not say it would do so.
IN PICTURES: Thailand's political crisis
Soldiers were seen in the heart of the capital's retail and hotel district and they surrounded the national police headquarters in the city centre, AP reported.
Thailand's army chief also ordered the censorship of the media in the interests of "national security", saying the army "prohibits all media outlets from reporting or distribution of any news or still photographs detrimental to national security."
But the city of 10 million people remained calm, with schools open and commuters driving and walking to work.
Sam Zarifi, Asian regional director at the International Commission of Jurists, called the declaration of martial law "confusing".
"There was already an emergency decree in place in Bangkok that provided security forces with significant authority to do what they wanted," he told Al Jazeera.
Thitinan Pongsudhirak, director of the Institute of Security and International Studies at Bangkok's Chulalongkorn University, said the key would be the role that the military played in politics.
"If they play the role of enforcer of law and order and even mediator...this could be a resolution to the impasse," Pongsudhirak said. But if they don't, "we can expect protests and turmoil from the losing side".
Civil war warning
The dismissal of Prime Minister Yingluck Shinawatra earlier this month in a controversial court ruling has raised tensions in the country, which has endured years of political turmoil.
Yingluck's "Red Shirt" supporters have warned of the threat of civil war if power is handed to an unelected leader, as demanded by the opposition.
Meanwhile, anti-government protesters refuse to participate in fresh elections and say Yingluck's Puea Thai party administration lacks the legitimacy to govern.
They are calling on the upper house of parliament, the Senate, to invoke a vaguely worded clause in the constitution to remove caretaker Prime Minister Niwattumrong Boonsongpaisan - an ally of Yingluck - and appoint a new leader.
Anti-government demonstrators, who had vowed a "final battle" in coming days to topple the prime minister, said they had called off a march that had been planned for Tuesday.
"We're convinced that invoking martial law will benefit our movement and support our goal," senior protest leader Sathit Wongnongtoey said.
Source: Al Jazeera and agencies