At least four people have been killed and several injured in the run-up to Liberia's presidential run-off.<br /><br />Thousands of opposition supporters clashed on Monday with riot police outside their party headquarters in the capital Monrovia.<br /><br />The main opposition party is boycotting the vote.<br /><br />Al Jazeera's Yvonne Ndege reports from Monrovia, Liberia.
