Malaysian police said Monday they have arrested five people after a group of protesters assaulted the Sri Lankan ambassador at Kuala Lumpur International Airport.

Malaysian authorities said the attack on High Commissioner (ambassador) Ibrahim Sahib Ansar on Sunday left him with minor injuries, but they have so far given no details on the identities or background of the attackers.

"Five people have been arrested and we are investigating the motive for the attack," Abdul Samah Mat, police chief of Selangor state, told AFP.

In Colombo Sri Lanka's Foreign Secretary Esala Weerakoon summoned Malaysia's top envoy, Wan Zaidi Wan Abdullah, and demanded adequate security for Colombo's diplomatic mission.

The foreign ministry expressed "disappointment that the Malaysian authorities had failed to provide necessary protection" despite warnings of a possible threat.

Almost 100 ethnic Indian protesters had gathered in Kuala Lumpur last week to rally against former Sri Lankan president Mahinda Rajapakse, who was attending an international conference, local media reported.

Rajapakse ordered the bloody military assault which ended Sri Lanka's war with Tamil separatist guerrillas in 2009.

International rights groups have said up to 40,000 civilians may have been killed in the final offensive, a charge denied by Colombo.

Sympathisers of the Tamil victims in the almost three-decade long civil war burnt an effigy of Rajapakse during the protests in Malaysia.

Police have warned local Indian groups not to show support for the Liberation Tigers of Tamil Eelam (LTTE) themselves.

"I want to warn these groups which support the LTTE that it is a group that is banned by the United Nations," national police chief Khalid Abu Bakar was quoted as saying by The Star on Monday.

More than two million of multi-ethnic Malaysia's 31 million people are ethnic Indians.

Most are descendants of labourers brought from ethnic Tamil areas of southern India by Malaysia's former British colonial masters.