Anti-government protesters in Thailand surrounded polling stations on Sunday, blocking early voting ahead of next week’s general election, officials said.Crowds of flag-waving demonstrators chained the doors of polling stations shut, despite promises by protest leaders not to obstruct the polls.Advance voting has reportedly been cancelled in a number of locations.Anti-government activists want Prime Minister Yingluck Shinawatra to step down and the political system to be reformed.The country’s election commission has called for the general vote scheduled for February 2 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.A state of emergency is in place as the authorities struggle to cope with the unrest.