Five people suspected of working for the Tamil Tiger rebels were killed in northeastern Sri Lanka when their grenades exploded before they could hurl them at a troop convoy, the military said Tuesday. But the rebels blamed the Sri Lankan military for Monday's incident in the port city of Trincomalee, according to a report of the Associated Press. The Liberation Tigers of Tamil Eelam said on its Web site that "a grenade was lobbed from an auto (motorized rickshaw) that drove past" the group of rebels. Quoting witnesses, the Tigers said after the grenade attack "the auto drove toward the Trincomalee Fort, where a Sri Lankan army camp is situated." Five Tamil students were killed by "Sri Lankan Special Forces," the Web site said without elaborating. Military spokesman Brig. Prasad Samarasinghe said it was a botched attack on an army patrol carried out by Tamil civilians who had been trained by the rebels "to attack military targets." Five of the seven alleged attackers died on the spot and the other two were wounded, Samarasinghe said. They had been sitting a few meters (yards) from a road frequented by military vehicles, he said. Investigators found a live grenade and the pin of the grenade that exploded at the blast site, suggesting that the grenade had not been thrown, he said. The rebels said all of the victims were under 20 and that all schools and colleges in the region were closed to protest the deaths. There was no independent account of what happened.