Thai authorities vowed today to get tough with anti-government Red Shirts paralysing central Bangkok, where protesters bracing for a crackdown reinforced their barricades and caused travel chaos. The Red Shirts have said they will turn up the heat on Prime Minister Abhisit Vejjajiva, sending out protesters on Wednesday to try to persuade more people to join their rally in the capital, which is under a state of emergency. The city's Skytrain service was halted for several hours today after Reds laid tyres on the rails at a station above the protest site to stop troops from using it for a surprise attack, forcing many commuters to walk to work. Services resumed after the protesters, who have been staging weeks of rolling rallies to campaign for snap elections, agreed to remove the tyres. The government said it would not tolerate moves by the opposition protesters to set up road checkpoints to prevent police and soldiers heading to the capital to reinforce security forces there.<br/>