Protesters have come out on the streets of the Sri Lankan capital, Colombo, to denounce a UN Human Rights Council resolution that has called for the government to fully investigate alleged war crimes during its offencive against Tamil Tiger rebels four years ago.

Rights groups said that in 2009, both sides committed atrocities, deliberately killing civilians as the army closed in on the last Tamil Tigers strongholds in northern Sri Lanka.

The government fought the Tamil rebels, who wanted an independent state, for more than 20 years.

One report suggested that as many as 40,000 civilians could have died in the final few months of the conflict.

Palitha Kohona, Sri Lanka's ambassador to the UN, spoke to Al Jazeera and explained his government's actions in investigating the war crimes.

Al Jazeera's Minelle Fernandez reports from Colombo.