An unidentified gunman opened fire at opposition protesters in Bangkok Saturday, killing one person and wounding several others in a pre-dawn attack that fanned tensions in the politically divided kingdom.

The shooting follows weeks of mass anti-government protests -- seeking to topple Prime Minister Yingluck Shinawatra -- that have triggered bloody clashes between police and demonstrators.

A protester died after he was shot in the torso and three others were hospitalised with gunshot wounds, a spokesman for the city's Erawan emergency centre said.

Police confirmed the shooting but said its forensic team was unable to access the scene of the incident, which happened where a group of protesters was camped overnight near Government House.

It was unclear who fired the shots but armed provocateurs have a history of trying to stir tensions in the politically polarised kingdom, with each side usually blaming the other.

Some local media reports said the shots were fired from a passing car by more than one gunman.

Yingluck has called February elections in the hope of bringing an end to the demonstrations, which have drawn tens of thousands of people seeking to curb her billionaire family's political dominance.

But the protesters have vowed to block the vote, saying it will only return the Shinawatra clan to power.

A second round of registration for constituency candidates was due to begin around the country on Saturday, raising fears of further clashes.

Eight people, including a policeman, have been killed and about 400 wounded in several outbreaks of street violence.

The government has said it will ask the army to provide security for election candidates and voters.

A policeman and a civilian died of gunshots fired by unknown assailants while 153 people were injured after violence erupted Thursday when demonstrators tried to force their way into an election registration venue.

The army chief insisted Friday that the military would remain neutral and said it was up to the election authorities whether the vote could go ahead, but he did not rule out another coup.

"The door is neither closed nor open. In every situation, anything can happen," he said when asked about the possibility of a coup, without elaborating.

Thailand has been periodically convulsed by political bloodshed since Yingluck's older brother Thaksin Shinawatra was overthrown by royalist generals in a coup seven years ago.

The protesters, a mix of southerners, middle class and urban elite, accuse the billionaire tycoon-turned-politician of corruption and say he controls his sister's government from his self-exile in Dubai.

They want an unelected "people's council" to run the country to oversee loosely-defined reforms -- such as an end to alleged "vote buying" -- before new elections are held in around a year to 18 months.

Yingluck's government still enjoys strong support in the northern half of the country and is expected to win the election if it goes ahead.

Thaksin's "Red Shirt" supporters have accused the demonstrators of trying to incite the military to seize power again, in a country which has seen 18 successful or attempted coups since 1932.

It is the worst civil strife since 2010, when more than 90 people were killed in a bloody military crackdown on pro-Thaksin Red Shirt protests under the previous government.