20 May 2014 Last updated at 07:18 ET
Why has Thailand imposed martial law?
The Thai army has imposed martial law following months of political unrest. Troops have been deployed across the capital, with sweeping new powers, but the army insists this is a not a coup. BBC News looks at why this has happened.
Why has martial law been declared?
The commander of the Thai army, General Prayuth Chan-ocha, said the presence of "ill-intentioned groups using weapons to threaten citizens" had justified the introduction of martial law.
But there have been months of political turmoil, and it is unclear why the military has suddenly decided to take this action now.
The anti-government protest movement had recently threatened to force the cabinet from office, but it has made similar threats many times before.
Last week three people were killed in an attack on an anti-government protest camp and the army warned of "decisive action" if the violence continued, but again there has not been an obvious trigger for Tuesday's announcement.
In pictures: Thailand comes under martial law
Is this a coup?
"This is not a coup," the army said in its declaration of martial law.
But to many Thailand watchers, it looks a lot like one. Brad Adams, Asia Director for Human Rights Watch, called it "a de facto coup."
Thailand's army has launched numerous coups in recent decades - there have been 11 since the end of absolute monarchy in 1932.
The latest coup was in 2006, when then Prime Minister Thaksin Shinawatra was toppled by the military after being accused of corruption.
The army is often accused of being sympathetic to the anti-government cause, but for now the government is insisting it is still in control, and that this is not a coup.
The BBC's Jonathan Head in Bangkok says much will depend on how much the army commanders work with the government, which has been trying to organise a date for a general election, or whether they decide to replace it.
What is happening on the ground?
Troops are patrolling the Thai capital, Bangkok, and key locations outside the city.
Roads have been blocked by tanks, and radio and TV stations have been closed. Soldiers have also moved into the main government building, which has been left unoccupied after months of demonstrations.
But daily life for the people of Bangkok remains largely unaffected. Schools, businesses and tourist sites are still open and traffic is moving as usual.
The pro-government movement, dubbed the Red Shirts, has said it will continue its rallies outside the capital, but has urged its followers not to challenge the soldiers.
What are the roots of the crisis?
There is a deep political divide in Thailand - between mostly rural, often poor, supporters of Mr Thaksin, and an urban middle class who object to what they see as his continuing influence in Thai politics.
There have been regular protests by both sides ever since Mr Thaksin was ousted in 2006, but in the past few years the focus has been on the current Thaksin-aligned Pheu Thai government.
The protests began to escalate into violence last November, after the lower house passed a controversial amnesty bill which critics said could allow Mr Thaksin to return from exile without serving time in jail.
The anti-government camp claims that at least 28 people have died since then.
The situation deteriorated still further earlier this month, when a controversial court ruling removed Mr Thaksin's sister Yingluck from her position as prime minister, saying she acted illegally by moving her national security chief to another position.
Profile: Yingluck Shinawatra
Where is Thailand heading after protests?
Who are the two sides?
The anti-government protesters are a disparate group, united by their opposition to Mr Thaksin.
They are being led by Suthep Thaugsuban, a former deputy prime minister who resigned from the opposition Democrat Party to lead the rallies.
The protesters say the Pheu Thai government has been buying votes with irresponsible spending pledges, aimed purely to bolster its support base, and thereby creating a flawed democracy.
They want the government dissolved and an interim administration appointed to oversee political reform.
In contrast, the Red Shirts have been largely supportive of the government's policies, and have warned that they will turn out in large numbers if the government they elected is forced from office.
They have held a number of rallies, but have for the most part remained off the streets.
Observers fear that if they were to decide to protest again, an escalation in violence would follow.
The Red Shirt leader, Jatuporn Prompan, said his group could accept martial law, but "would not tolerate a coup or other non-constitutional means'' to take power.
