A five-year-old girl was killed and 30 other people were wounded after gunmen sprayed bullets on an anti-government rally in eastern Thailand, police said Sunday.

The attack marks the latest flaring of political violence in the deeply polarised kingdom, where months of anti-government rallies have been marred by sporadic gun and grenade attacks by unknown assailants.

Gunmen on two pick-up trucks opened fire on a packed market place late Saturday in Khao Saming district of Trat province where an anti-government rally was taking place, according to police lieutenant Thanaphum Naewanit.

"A five-year old girl was shot and died later while 30 other people were injured," he said, adding the shooting was believed to be politically motivated.

"The aim was to disturb the rally," he said.

Television footage showed dozens of upturned plastic chairs at the rally site and abandoned street stalls after people fled the shooting in panic.

Fears of widespread violence have intensified in step with ongoing protests to topple Prime Minister Yingluck Shinawatra, with tensions soaring on both sides of Thailand's stark political divide.

Most of the violence has taken place in or around Bangkok, where protesters are carrying out a self-styled "shutdown" of several key intersections across the city centre.

Seventeen people have been killed, both protesters and policemen, and hundreds injured in gunfire and grenade blasts linked to demonstrations.

New York-based Human Rights Watch accused both police and protesters of using live ammunition in clashes last week in Bangkok's historic district in which five people were killed and dozens wounded.

Yingluck is under intense pressure from various legal challenges as well as the street protests demanding her resignation.

She faces charges of neglect of duty over a controversial rice subsidy scheme that could see her removed from office.

Protesters accuse Yingluck's billionaire family of using taxpayers' money to buy the loyalty of rural voters through populist policies such as the rice scheme.

They are demanding she steps down to make way for a temporary unelected council that would oversee loosely defined reforms to tackle corruption and alleged vote-buying.

Her government was last week also banned from using force against peaceful demonstrators by a court ruling which government officials said crippled their powers to handle the mounting violence.

Thailand has been scored by deep political divisions since a military coup in 2006 ousted then-premier Thaksin Shinawatra -- Yingluck's older brother.