United Nations Secretary General Ban Ki-moon has expressed alarm at the violence surrounding the run-up to Sri Lanka's presidential election. He has urged all political parties and their supporters to refrain from violence and to avoid provocative acts throughout the election period. <br/><br/>At least four people have been killed in poll-related violence in the weeks leading up to the election. The 26 January vote is taking place amid heightened tension. Gen Sarath Fonseka, Sri Lanka's former army chief is the main rival to President Mahinda Rajapaksa.<br/><br/>He resigned from his post as chief of defence staff in November following differences with the government over who should take credit for defeating the Tamil Tiger rebels last May.