COLOMBO (AFP) - Dozens of Sri Lankan nationalists rallied outside the United Nations compound in Colombo on Thursday (Sept 1) as Secretary-General Ban Ki Moon visited the island, protesting against the UN's actions during a prolonged civil war.

Police held back the demonstrators led by Buddhist monks as they tried to march on the compound just before Mr Ban arrived on the first full day of his two-day visit to Sri Lanka.

"UN, where were you?" said one placard, which carried a photograph of a victim of a bombing blamed on Tamil Tiger rebels who were crushed by security forces in May 2009.

The protesting ultra-nationalists accuse the UN of siding with Tamil rebels while hardliners in the Tamil community also criticise it for failing to protect civilians during Sri Lanka's 37-year ethnic war.

"The UN was silent when Tiger terrorists were bombing and massacring our people," Buddhist monk Akmeemana Dayaratne said as protesters handed over a petition to the UN office to be given to Ban.

"Now the UN is asking for investigations to punish us for defeating terrorism," he said, referring to the UN's call for the island to probe war crimes committed during the conflict.

A police official outside the UN offices, located in a tightly guarded area of the capital, said officers had obtained a court order preventing protests to avoid breaches of the peace.

"We did that because we feared that any protest could lead to unrest," he said, requesting anonymity.

Mr Ban's convoy arrived at the compound shortly after the protesters had been peacefully dispersed.

The UN leader held talks with Prime Minister Ranil Wickremesinghe on Wednesday evening after arriving in Sri Lanka from Myanmar, and is due to meet with President Maithripala Sirisena later on Thursday.

He is also due to deliver a public lecture on peace and development and travel to the war-battered northern Tamil heartland of Jaffna, before leaving on Friday.

Sri Lankan diplomats said they were keen to discuss the new government's reconciliation efforts following the civil war that claimed at least 100,000 lives between 1972 and 2009.

The UN has been pushing for a special court to investigate allegations that up to 40,000 Tamil civilians were killed by government forces in the final months of fighting.

Mr Sirisena, a member of the majority Sinhalese community who came to power in January last year, has pledged to punish those responsible for war crimes during the conflict.