A loud blast shook the house of a senior Thai opposition leader overnight, police said on Wednesday, as protesters trying to oust the government remained camped in central Bangkok with no end to the political deadlock in sight.Some hardline protesters have threatened to blockade the stock exchange and an air traffic communications facility on Wednesday if Prime Minister Yingluck Shinawatra does not step down.But there were no early signs of trouble at either the bourse or at the central Bangkok offices of AeroThai, which is in charge of air traffic control for planes that use Thai air space.No one was hurt in the blast at the residence of Democrat Party leader and former Prime Minister Abhisit Vejjajiva."There was no one at home at the time. The explosion destroyed part of the roof of the house. It wasn't a bomb. We believe it could have been a big firework," said an officer at the nearby Thong Lor police station, declining to be named.Abhisit and other Democrat leaders have joined in the protest movement against Yingluck, and have refused to take part in an election she has called for Feb 2.She has invited leaders of the protest movement and political parties to a meeting on Wednesday to discuss a proposal to postpone the election, but it looked like only her allies would turn up.The unrest is the latest chapter in an eight-year conflict pitting the Bangkok-based middle class and royalist establishment against the mostly poorer, rural supporters of Yingluck and her brother, Thaksin Shinawatra, a former premier ousted by the military in 2006 who is seen as the power behind her government.Abhisit was prime minister in 2010 when troops were sent in to end a two-month protest in central Bangkok by Thaksin supporters. More than 90 people died during those protests.Current protest leader Suthep Thaugsuban was one of his deputies at the time and oversaw security matters during the 2010 crackdown. Both now face murder charges.The latest protests have been relatively less violent. Eight people, including two police officers, have been killed and scores wounded in violence between protesters, police and government supporters since the trouble flared up in November.National Security Council chief Paradorn Pattanathabutr said two protesters were slightly injured overnight when shots were fired by the Siam Discovery mall near the main protest camp. One man was shot in the ankle and a woman was hit by a ricochet.No one was arrested.Yingluck's meeting on the election date will be held at the air force headquarters in the north of the city. She has been unable to work from her office in Government House since late November because of the protests.Suthep's supporters have blockaded at least seven big intersections in Bangkok and are also trying to stop ministries from functioning, forcing many to remain closed, with civil servants working from back-up facilities or from home.Protest leaders say demonstrators will occupy the city's main arteries until an unelected "people's council" replaces Yingluck's administration, which they accuse of corruption and nepotism.Yingluck's Puea Thai Party seems certain to win any election held under present arrangements and Suthep's central aim is to alter the electoral rules to make a different outcome possible.