The rebel Liberation Tigers of Tamil Eelam (LTTE) said five civilians, including a businessman, were killed by security forces while the sixth, a student, was killed in a mortar bomb attack by troops.

The LTTE also said security forces had killed 66 civilians last month, and blamed the forces for the "disappearance" of another 62 Tamils, claims denied by the military.

The military said the Tigers had kept up artillery and mortar attacks against security forces in the island's northern and eastern regions at the weekend and troops retaliated.

The defence ministry said top commanders visited the restive eastern province on Saturday to discuss "the security measures to be taken against the LTTE atrocities in the area."

Elsewhere, security forces in the northern town of Vavuniya on Sunday found two Tamil labourers shot in the head, local officials said.

Near the capital Colombo, police on Saturday found five men shot in the head after being blindfolded in an apparent execution-style killing. An investigation is underway.

The grisly find in a marsh at Kandana, 15km north of the capital, was made after a child spied one of the bodies, a police spokesman said.

Both local and international human rights activists have said abductions and killings are rampant in Sri Lanka amid an escalation of fighting between government troops and Tamil Tiger rebels in a 35-year-old ethnic conflict.