Bangkok - Thailand's army declared martial law on Tuesday after months of deadly anti-government protests, deploying armed troops in central Bangkok and censoring the media but insisting the move was "not a coup".
Gun-wielding soldiers and army vehicles were seen in the heart of the capital's retail and hotel district. Troops were also positioned at TV stations where broadcasts were suspended under sweeping censorship orders.
The dismissal of prime minister Yingluck Shinawatra earlier this month in a controversial court ruling has sent tensions soaring in the kingdom, which has endured years of political turmoil.
"Red Shirt" supporters of Yingluck and her brother Thaksin Shinawatra, who was deposed as premier in a 2006 coup, have warned of the threat of civil war if power is handed to an unelected leader, as the opposition demands.
Thailand has been without a fully functioning government since December, disrupting government spending, spooking investors and deterring foreign tourists.
The United States, a key ally of Thailand, said the use of martial law must be "temporary" and urged all parties "to respect democratic principles".
Southeast Asia's second-biggest economy is hurtling towards recession and Japan, whose companies have some of the biggest foreign investment in Thailand, also expressed "grave concerns" at the unfolding crisis.
As troops took to the streets around Bangkok, the leader of the Red Shirt movement said soldiers had encircled their protest on the western outskirts of the capital, and the government said the military was trying to convince them to disperse.
"We have been surrounded by troops on all sides," Jatuporn Prompan told AFP.
'No need to panic'
An announcement on military-run television said martial law had been invoked "to restore peace and order for people from all sides" after nearly seven months of protests that have left 28 people dead and hundreds wounded.
"This is not a coup," it said. "The public do not need to panic but can still live their lives as normal."
Despite the assurances, concerns a military takeover was under way were fuelled by the troop presence and an order from army chief General Prayut Chan-O-Cha that media would be censored in the interests of "national security".
Broadcasts were suspended at several television stations including three pro-government channels as well as the anti-government camp's Blue Sky TV - which has aired protests round-the-clock and been key in galvanising rallies.
"I think what we are looking at is a prelude to a coup. That is for sure. It is all part of a plot to create a situation of ungovernability to legitimise this move by the army," said Pavin Chachavalpongpun from the Centre for Southeast Asian Studies at Kyoto University.
The country's embattled government was not consulted in advance about the imposition of martial law, said Paradorn Pattanatabut, chief security adviser to new prime minister Niwattumrong Boonsongpaisan.
"The caretaker government still exists with Niwattumrong as caretaker prime minister. Everything is normal except the military is responsible for all national security issues," he said.
A top aide to the premier said they were holding a "mini-cabinet meeting now in a safe house" and would make an official announcement later in the day.
On the streets of the capital, where a military crackdown on Red Shirts protests in 2010 under the previous government left dozens dead, life mostly went on as usual.
Thais have become accustomed to political upheaval, although there was confusion and nervousness over how the crisis will unfold.
"What a chaotic situation," said Chitra Hiranrat, aged 49, as she waited for a motorcycle taxi to go to work.
"I don't know what else we'll have to face in the future. Whether martial law will be helpful or not I can't say because it's only the first day. Let's wait and see," she said.
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.
Under Thailand's constitution, the military has the right to declare martial law - which gives the armed forces control of nationwide security - if urgently needed.
But the move risks angering supporters of the government if it is seen as tantamount to a coup.
Thailand's army previously declared martial law in September 2006 following the bloodless military coup that ousted Thaksin Shinawatra - the latest in a total of 18 successful or attempted coups the country has seen since 1932.
Anti-government protesters refuse to participate in elections without political reforms first, and say Yingluck's Puea Thai party administration lacks the legitimacy to govern.
An election held in February was annulled after demonstrators blocked voting, and new elections scheduled for 20 July look in grave doubt.
Despite the dramatic events, the Thai bourse slipped just 0.75% with some analysts suggesting the move could help break the crippling deadlock which saw the economy shrink 0.6% in the first quarter year-on-year, the first such contraction since 2011.