At least five Sri Lankan sailors have been killed and 10 are missing after a navy boat was ambushed by suspected Tamil Tiger rebels, officials say. A loud explosion rocked the port of Trincomalee, in the north-east of Sri Lanka, shortly after two patrol boats left the harbour on Friday night. The incident would be the latest in a series of attacks by the separatist Tigers against military targets. A navy spokesman told the Reuters news agency they suspected a suicide attack. The recent attacks by Tamil Tiger rebels have raised fears that Sri Lanka may be sliding back into civil war after four years of an officials ceasefire.