Gun battles between anti-government demonstrators and police in Bangkok have reportedly left an officer and three protesters dead and dozens of people wounded.
It came amid a major operation involving some 15,000 police officers to clear the capital’s streets of protests.
A medical centre which monitors hospitals said three demonstrators were killed by gunfire.
One policeman appeared to have been shot in the head. The national police chief Adul Saengsingkaew confirmed an officer had died, saying he had succumbed to his injuries on the way to hospital.
Witnesses said they saw firearms being carried by both sides.
But the head of Thailand’s National Security Council, Paradorn Pattanathabutr, insisted the police were armed only with batons and riot shields, did not use rubber bullets, and accused protesters of using tear gas.
Police said around 100 people were arrested at one site alone, near the Energy ministry.
Eight years of on-off protests have pitted the Bangkok middle class and royalist establishment against the poorer, mostly rural supporters of Prime Minister Yingluck Shinawatra.
Her critics believe her older brother Thaksin – toppled from power in 2006 – is pulling the strings behind the scenes.