Media playback is unsupported on your device Media caption The BBC's Jonathan Head: "The protesters are showing that they can sabotage an election"

Protesters in Thailand have surrounded polling stations, blocking early voting ahead of next week's general election, officials say.

One of their leaders has been shot dead during a clash with government supporters in eastern Bangkok.

Advance voting has been cancelled in dozens of venues in the capital and several southern provinces.

Anti-government activists want PM Yingluck Shinawatra to step down and the political system to be reformed.

Analysis Thailand's protest movement has an image problem. It is commonly viewed outside Thailand as undemocratic. The movement's leader, Suthep Thaugsuban, even wrote a letter to US President Barack Obama this week pleading for more understanding of his goals. But the scenes of his supporters forcefully blocking people from voting won't help that negative image. Mr Suthep's promise, that the demonstrations would not obstruct the voters, was broken repeatedly. In some areas, election officials appeared almost eager to comply with the protesters, fuelling suspicion among the government's supporters that the purportedly independent Election Commission is taking sides. The government says the main polling day next Sunday will go ahead as scheduled. The Election Commission says it should not. They will meet to discuss the timing on Tuesday. Neither outcome will address the bitter polarisation of Thai society. Each side increasingly demonises and dehumanises the other - even more so after a well-known protest leader was killed in a confrontation that turned ugly outside a polling station.

Suthin Taratin was speaking on top of a truck, which was part of a rally at a polling station where advanced voting was supposed to take place, when he was struck by gunfire, reports the BBC's Jonathan Head in Bangkok.

He died later in hospital.

Crowds of flag-waving demonstrators chained the doors of polling stations shut, despite promises by protest leaders not to obstruct the polls.

The protesters surrounded polling stations in Bangkok and southern Thailand in an attempt to stop people voting.

Voting was either blocked completely or halted at 49 out of 50 polling stations in Bangkok. Early voting was also disrupted in 10 of Thailand's 76 provinces, reports said.

The election commission has called for the general vote scheduled for 2 February to be postponed because of possible disruption and violence.

But the government has so far insisted that the election must go ahead on schedule.

The latest disturbances comes despite a pledge from protest leader Suthep Thaugsuban, who said on Saturday that his supporters would not obstruct advance voting - although they would demonstrate outside polling stations.

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The protest movement says it is not obstructing the poll, but that "supporters are simply protesting the advance polls held today by surrounding/standing in front of election units", in a statement on its Facebook page.

Advance voting is for those unable to take part in the February election.

A state of emergency is in place as the authorities struggle to cope with the unrest.

Protesters, who started their campaign in November, want to install an unelected "people's council" to run the country until the political system is changed.

They say Ms Yingluck's government is being influenced by her brother, exiled former leader Thaksin Shinawatra.

At least nine people have died since the wave of protests started last year.