Sri Lanka's [Images] warplanes on Saturday attacked a suspected base of Tamil Tiger suicide cadres in the island's northern region, the defence ministry said.

It said the outfit's suicide squad Black Tigers was targeted.

It did not give details of any casualties.

However, the ministry said they caused "heavy damages".

The attack came as the Tigers commemorated their war dead. Tiger chief Velupillai Prabhakaran who turns 52 on Sunday is to make his annual speech on Monday.

Meanwhile, a policeman was killed when he was caught up in a land mine attack in the northern district of Vavuniya.

In the island's east, the military claimed killing four rebels.

The LTTE said they had decorated areas under their control with red and yellow flags to mark Heroes' Week ending on Monday.

The pro-rebel tamilnet.com website said the military was moving to disrupt commemorative events inside government-held areas of Sri Lanka's northern Jaffna peninsula.

"Sri Lanka army troopers, Thursday and Friday, have destroyed the platforms erected for the celebrations in the three Heroes' cemeteries and also have razed to the ground several memorial stones," tamilnet.com said.

Fighting between the Tigers and government troops has escalated in the past year, claiming more than 3,400 lives despite a now threadbare ceasefire agreed in 2002.