The Sri Lankan Navy foiled an attack by Tamil Tiger rebels on a food ship and destroyed at least three of their boats off the north coast on Sunday, a military spokesman said. The ship, 'City of Liverpool' had unloaded food stocks and was travelling to Kankasanthurai harbour, 410 kilometres north of Colombo, when it was attacked, he said. At least 15 to 20 rebels were involved in the attack. Six boats had followed the ship and one of them had exploded nearby causing damage to it.City of Liverpool'At least three rebel boats were destroyed but details of the casualties were not known immediately. Three sailors were injured,' the spokesman said. The ship has been towed to safety. The government has been sending food to northern Sri Lanka by ship since last August after the main highway to the region was closed in the wake of battles with the rebels of the Liberation Tigers of Tamil Eelam.