COLOMBO — Defence Secretary Liam Fox has urged the Sri Lankan government to investigate war crimes alleged to have been committed during the island's separatist conflict with Tamil rebels.

The British High Commission said Liam Fox had pushed Sri Lanka, a former British colony, to probe the charges of deliberate bombing of civilians and unlawful killings.

"Allegations of violations of international human rights and humanitarian law by both sides at the end of the conflict (must) be taken seriously," Fox said on Saturday.

Sri Lankan troops defeated the Tamil Tiger guerrillas in 2009 in a major offensive that attracted widespread allegations that tens of thousands of civilians were killed in the fighting.

Fox, who was in Colombo to deliver a lecture in memory of slain Sri Lankan foreign minister Lakshman Kadirgamar, said the allegations must be "fully investigated and any individuals responsible brought fully to account".

Kadirgamar, a personal friend of Fox, was assassinated by suspected Tamil Tiger rebels in 2005.

Fox said Sri Lanka needed to address national reconciliation to emerge after decades of ethnic strife.

"A genuine peace requires... freedom from fear, freedom of expression including a free press and broadcast media and the freedom to dissent within the law," he added.

Britain and the United States have led international calls for accountability and media freedom in Sri Lanka, where more than a dozen journalists and media workers have been killed in the past decade.

Fox's remarks came after police detained a British citizen of Sri Lankan origin on charges that he provided videos to Britain's Channel 4 television for its controversial documentary "Sri Lanka's Killing Fields".

Sri Lanka has persistently denied that its troops committed any war crimes while defeating the Tamil Tiger rebels.