COLOMBO, SRI LANKA, OCT. 5 -- Twelve Tamil separatist guerrillas committed suicide today in the northern city of Jaffna as government troops were taking them to be questioned about alleged arms smuggling.

A government official said 17 members of the Liberation Tigers of Tamil Eelam swallowed cyanide capsules at Jaffna's airport as they were about to be flown to Colombo, the capital. He said the men were taken to an Army hospital where 12 died and the others were in critical condition.

The 17 had been arrested for smuggling arms from Jaffna, a Tamil guerrilla stronghold in the north, to the eastern city of Trincomalee, where members of the minority Tamils have been fighting residents of the majority Sinhalese community for the past six days. The Liberation Tigers, in a statement released by its office in Madras, India, denied that the men had smuggled arms and said they had "swallowed the cyanide in true heroic {Tigers'} spirit."

Indian peace-keeping troops have failed to halt the Trincomalee clashes, which have killed about 18 people. Government officials have charged the Liberation Tigers with attacking Sinhalese and Moslems in the Trincomalee area to drive them out.

President Julius Jayewardene ordered additional Indian peace-keeping troops to Eastern Province over the weekend to quell the violence in Trincomalee, where Tamils, Sinhalese and Moslems live in roughly equal numbers.

Under a peace agreement between India and Sri Lanka, the north and east will be joined in a single semiautonomous area, but residents of Eastern Province will vote next year whether to remain linked to the Tamil-dominated north.