Thailand police and protesters collide in Bangkok
Police are trying to retake official buildings and sites that have been blocked by demonstrators.
Earlier on Tuesday, they arrested around 100 protesters outside a ministry building.
Thailand has been embroiled in a political crisis since anti-government protests began in November.
Demonstrators have occupied official sites over the past few months, calling on the government to step down. The government has announced that it wants to retake all the besieged buildings this week.
The prime minister’s office, Government House, has been a focal point for the demonstrators. Thousands gathered outside the building on Monday, cementing the gates shut in a bid to stop officials returning to work.
Early on Tuesday, police started negotiations with the protesters, who over the past few days have come in large numbers to defend protest areas.
Violence then erupted in one part of central Bangkok. One police officer was shot dead, police said. Gunshots have been heard in the capital, although it is not clear who was firing.
The city’s Erawan emergency medical centre said that more than 40 people were injured, although it did not report the breakdown between police and protesters.
There are also reports of police being injured by shrapnel from bomb blasts.
Elsewhere, police reclaimed the besieged Ministry of Energy, with around 100 protesters arrested.
‘Enemy of the people’
To date, police have been reluctant to use force against the protesters. They have previously allowed demonstrators to enter government buildings in a bid to defuse tensions.
Anti-government protesters want Prime Minister Yingluck Shinawatra to step down, alleging that she is controlled by her brother, former leader Thaksin Shinawatra, who is currently in self-imposed exile.
They want her government to be replaced by an unelected “people’s council” to reform the political system.
On Tuesday, protest leader and former opposition politician Suthep Thaugsuban said in an address to police: “We are not fighting to get power for ourselves.”
“The reforms we will set in motion will benefit your children and grandchildren, too. The only enemy of the people is the Thaksin regime.”
Ms Yingluck leads a government that won elections in 2011 with broad support from rural areas. In response to the protests, she called snap elections on 2 February, which her government was widely expected to win.
However, the polls were boycotted by the opposition, and voting was disrupted by protesters at around 10% of polling stations, meaning by-elections are needed before a government can be formed.