Government supporters and opposition activists have clashed during a demonstration outside the Sri Lankan supreme court in the capital Colombo.

The protesters were demanding the immediate release of former Sri Lankan army leader Sarath Fonseka, who was arrested on Monday. Riot police used water cannon and tear gas to disperse the crowds. Several bystanders were reportedly injured by flying stones.

General Fonseka is being held at the headquarters of the Sri Lankan navy. The opposition fears his life may be in danger there. The general is accused of plotting against the state. He was President Mahinda Rajapaksa's main rival in the presidential elections two weeks ago.

General Fonseka worked closely with President Rajapaksa to defeat the Tamil Tigers last May, bringing the rebels' 25-year struggle for independence to an end. Both men claim responsibility for the victory.