The moment the small group of Thai red-shirts breached parliament
Thousands of Thai anti-government protesters - known as "red-shirts" - have marched on parliament, amid high political tension in Bangkok.
The red-shirts forced MPs to call off a session and some breached security to enter parliament's grounds, but they have now pulled back.
They want Prime Minister Abhisit Vejjajiva to resign and call elections.
Thailand has lurched from one crisis to another since 2006 when the government of Thaksin Shinawatra was overthrown.
The BBC's Rachel Harvey in Bangkok says the current bout of red-shirt rallies - which began on 12 March - has no end in sight.
She says businesses which were forced to close by the rallies have now begun to reopen - a sign that the capital's residents accept the protests will be long term.
The government has vowed not to use force against the red-shirts, and the protesters too have promised to keep the demonstrations peaceful.
But analysts say Mr Abhisit is coming under increasing pressure from his supporters to toughen his stance.
Many rural dwellers and urban poor support
red-shirts, while yellow-shirts comprise mainly middle classes and urban elite
September 2008 yellows rally against government, reds counter-rally, clashes in Bangkok
Yellows blockade airport in
November 2008, government collapses, yellow-friendly government installed
April 2009 red protests halt Asean summit, two people die in Bangkok clashes, rallies called off
Reds relaunch protests in
March 2010, splash blood on government buildings, march on parliament
Thousands of red-shirts - many of whom support Mr Thaksin - gathered outside parliament on Wednesday, and were faced with similar numbers of riot police.
The parliamentary session was abandoned shortly after it had begun and senior politicians, including Mr Abhisit, were ushered out of the building by security guards.
While some MPs used ladders to scale walls as they escaped parliament, others were picked up by a military helicopter which landed on the roof of the building.
A group of protesters then managed to barge their way into the grounds of parliament, but retreated shortly afterwards and there were no reports of violence.
The protesters, whose official title is the United Front for Democracy Against Dictatorship (UDD), are stepping up their campaign to force Mr Abhisit to call an election.
They say they will not move from Bangkok until their demands are met.
Last week the two sides held talks but discussions broke up without resolution.
Most of the support for the red-shirts comes from rural areas and the urban poor, who benefited from many of Mr Thaksin's populist policies.
On the other side of Thailand's political divide, the urban middle classes and traditional political elite - who protest dressed in yellow - back the current government.
Mr Abhisit came to power shortly after weeks of protests by yellow-shirts had paralysed the country.