Colombo - Sri Lanka's opposition leader Ranil Wickremesinghe Tuesday called for an international investigation into Monday's suicide attack, which killed 28 people in the North Central province.

Former prime minister Wickremesinghe told parliament in a statement that he was not satisfied with the local investigations and asked foreign experts to investigate the attack, which killed retired Major General Janaka Perera and 27 others.

The opposition leader blamed the government for failing to provide sufficient security after a suspected Tamil rebel suicide bomber detonated himself.

"The government failed to provide adequate security to the former retired army officer who was a target of the LTTE," Wickremesinghe said, referring to rebels of the Liberation Tigers of Tamil Eelam (LTTE).

Perera, his wife, as well as an opposition activist and his wife, were among about 300 others taking part in a ceremony to establish an office for the opposition United National Party in Anuradhapura, 180 kilometres north of Colombo. Among them, 94 were injured.

Prime Minister Ratnasiri Wickremanayaka said a full investigation would be held regarding the attack.

Monday's attack came as government troops moved closer to a rebel-occupied town of Kilinochchi, 380 kilometres north of Sri Lanka. The majority of residents have fled the area.

The prime minister told parliament Tuesday that 200 soldiers and police were killed in military operations in the north and 997 security personnel were injured in battle last month.

However, he did not disclose the number of rebels killed. (dpa)