Thai police fired tear gas and rubber bullets Thursday as clashes broke out with protesters trying to prevent political parties registering for elections, leaving dozens wounded and forcing officials to flee by helicopter.
Prime Minister Yingluck Shinawatra has faced weeks of mass street rallies seeking to curb her family's political dominance and install an unelected "people's council" to oversee electoral reforms.
Fresh violence erupted as demonstrators tried to force their way into a sports stadium in the capital where representatives of about 30 political parties were gathered for the registration process for February 2 elections.
Thirty-two people were hospitalised, including one protester who was in a serious condition with an apparent gunshot wound to his head, a senior official at the public health ministry, Supan Srithamma, told AFP.
"It's likely that he was shot by a live bullet," he said.
Police said three of their officers were wounded including one who was struck by a bullet in his arm.
Security forces denied firing live rounds, saying only rubber bullets and tear gas were used against the demonstrators.
"Protesters are not peaceful and unarmed as they claimed," deputy prime minister Surapong Tovichakchaikul said in a televised address.
"They are intimidating officials and trespassing in government buildings."
Several election commissioners were airlifted from the stadium by helicopter while other officials, party representatives and journalists were trapped inside.
Thailand has seen several bouts of political turmoil since Yingluck's older brother Thaksin Shinawatra was ousted as premier in a military coup in 2006.
His supporters have accused the protesters of trying to incite the military to seize power again, in a country which has seen 18 successful or attempted coups since 1932.
The political conflict broadly pits a Bangkok-based middle class and elite against rural and working-class voters loyal to Thaksin, who lives in self-exile.
The protesters accuse the billionaire tycoon-turned-politician of corruption and say he controls his sister's government from his base in Dubai.
The unrest, which has drawn tens of thousands of protesters onto the streets, has left five people dead and more than 200 wounded.
It is the worst civil strife since 2010, when more than 90 civilians were killed in a bloody military crackdown on opposition protests against the previous government.
Yingluck has called a snap election for February 2 to try to resolve the deadlock, but the main opposition Democrat Party -- which has not won an elected majority in about two decades -- has vowed to boycott the vote.
The demonstrators have vowed to keep up their campaign to disrupt the polls, with protest leader Suthep Thaugsuban threatening to "shut down the country" to prevent people voting.
A second round of registrations for constituency candidates is due to begin at venues around the country on Saturday.
Yingluck's Puea Thai party said it planned to field candidates in all constituencies, despite the prospect of further attempts by the opposition to disrupt the process, particularly in its southern strongholds.
"If there is a problem we have to fight," Puea Thai leader Jarupong Ruangsuwan told AFP.
Thaksin is adored among rural communities and the working class, particularly in the north and northeast. But he is reviled by the elite, the Bangkok middle class and many southerners, who see him as corrupt and a threat to the revered monarchy.
Pro-Thaksin parties have won every election since 2001, most recently with a landslide victory under Yingluck two years ago.
The protesters want loosely-defined reforms -- such as an end to alleged "vote buying" -- before new elections are held in around a year to 18 months.
Critics argue that the planned changes are only aimed at ending the opposition's losing streak.
Yingluck on Wednesday proposed a "national reform council" made up of 499 representatives from various sectors to recommend constitutional amendments and economic and legal reforms, as well as anti-corruption measures.
But the protesters quickly rejected the idea, urging her to step down.