The Sri Lankan navy and air force have attacked boats belonging to Tamil Tiger rebels off the northwestern coast, sinking at least one of them.
A government spokesman says Sri Lanka's navy and airforce returned fire today (Friday) after the rebel boats attacked two navy patrol boats.
Sri Lankan officials say one of the rebel boats exploded during the clash, indicating that the boat was packed with explosives and may have been intended for a suicide attack.
The officials say some of the rebels fled back to shore and clashed with government troops there.
The clashes came as Japanese mediator Yashusi Akasi was due to arrive in Sri Lanka for meetings with President Mahinda Rajapakse and, separately, with Tamil leaders. Japan is Sri Lanka's biggest donor and Akasi is expected to try to salvage a shaky four-year-old cease-fire accord.
More than 150 people have been killed in clashes between the government and Tamil rebels since April, threatening the 2002 ceasefire.
Peace talks were due to open in Switzerland last month but were called off amid escalating violence.
More than 60-thousand people have been killed in the 20-year conflict between the Sri Lankan government and Tamil rebels fighting for autonomy.