Colombo : Sri Lanka's President Mahinda Rajapaksa is to officially announce the end of the 25-year civil war against Tamil rebels, a day after top rebel leaders including commander Velupillai Prabhakaran were killed by the military.

In an address to the nation Tuesday morning, scheduled for 0400 GMT at Parliament, Rajapaksa is expected to make the announcement to be broadcast live on television and radio stations.

Streets, homes and government buildings in Colombo were decked out with national flags as celebrations were organized to mark the end of the war, in which more than 80,000 people lost their lives and many thousands more were maimed and wounded.

A government statement appealed to the public to fly the national flag in all houses and institutions, "as a mark of victory achieved by security forces in defeating terrorism and as a tribute to heroic soldiers who sacrificed their lives for the nation."

On Monday evening, Defence Secretary Gotabaya Rajapaksa and the commanders of the army, navy, air force and police met with Rajapaksa to inform him about the offensive against the Liberation Tigers of Tamil Eelam (LTTE).

Military operations against the rebels were halted Monday noon after the army confirmed that as many as 18 of most senior LTTE leaders were killed.

Among those killed were Prabhakarn's son Charles Anthony, deputy LTTE leader and intelligence chief Pottu Ammna, and the rebels' navy commander Sooai.

Other senior LTTE members reported killed were politcal division head P Nadesan, S Pulidevan, the head of the Tamil Tiger's peace secretariat and Kapil, who was in charge of the LTTE police wing.

According to ground troops, Prabhakarn was trying to flee the combat zone in an ambulance when the vehicle was hit by the army and caught fire in the incident. The leader's body was burned.

As many as 250 rebels were killed in the final confrontation at Vellamulliavaikkal, 395 kilometres north-east of the capital.

With the end of the conflict, focus shifts toward the 250,000 civilians who fled the rebel-held area and now live in government camps in the Northern Province.

UN Secretary General Ban Ki-moon is due in Sri Lanka Friday to assess the humanitarian needs. (dpa)