COLOMBO, Sri Lanka -- A bomb ripped through a packed civilian bus Wednesday, killing 23 people in southeastern Sri Lanka as the government officially withdrew from a tattered cease-fire with Tamil Tiger rebels.

The blast, the latest in a string of attacks in government-held territory in recent months, struck the bus in the remote town of Buttala, about 150 miles southeast of Colombo.

Doctors from Colombo were being flown to the area by emergency helicopters, government officials said.

It was unclear if the bomb was on the bus or planted by the roadside, said military spokesman Brig. Udaya Nanayakkara. In addition to the 23 killed, 67 people were injured, he said.

Senior Superintendent Daya Samaraweera, a local police official, said the blast was caused by a roadside bomb and it was followed by a volley of gunshots fired at the bus.

The 8 a.m. explosion came just hours after the official end of the 2002 cease-fire agreement, which had largely broken down over the past two years amid renewed fighting.

Though scrapping the truce has little direct impact on the raging war, the Cabinet's unanimous decision to end the deal was criticized by peace mediators and foreign governments as a move that would make it even more difficult to end the decades-old conflict.

In the two weeks since the government told officials from Norway, a key broker of the deal, that it would end the cease-fire Wednesday, more than 300 people have been killed in violence along the front lines in the north, according to military figures.

The most immediate effect of the end of the cease-fire is the dissolution of the Sri Lankan Monitoring Mission, one of the few independent groups with access to both rebel-held territory and the government.

The Tamil Tigers have been fighting since 1983 for an independent state for Sri Lanka's ethnic Tamil minority in the north and east after decades of being marginalized by Sinhalese-dominated governments. The fighting has killed more than 70,000 people.

President Mahinda Rajapaksa has said he abandoned the cease-fire because it wasn't working and the rebels used it as cover to build up their military strength. At least 5,000 people have been killed since the cease-fire was signed.

The cease-fire was hailed as a crucial step toward ending the fighting when it was initiated in 2002 and for several years the violence plummeted and trade and travel flowed easily across the frontier between the rebel's de facto state in the north and government-held territory.

But new fighting broke out two years ago, leading to a wide-scale government offensive that forced the rebels out of the cities and towns of the east in July.

Japanese peace envoy Yasushi Akashi, who rushed to Sri Lanka for talks before the cease-fire expired, said Tuesday his country was concerned that the end of the truce would lead to even greater violence and more civilian casualties. Discuss this story Published: Tue Jan 15 23:34:50 EST 2008

President Mahinda Rajapaksa's government said the truce, brokered by Norway, will formally end today because the LTTE used it to boost its forces and prepare attacks. The Tamil Tigers last week said they were ``shocked and disappointed'' by the decision.

``The cease-fire ended quite some time ago when the LTTE unilaterally returned to full-scale hostilities in December 2005,'' Sri Lanka's mission to the UN in Geneva said in a statement yesterday.

Sri Lanka's army has driven Tamil Tiger forces from the eastern region, leaving the group in control of bases only in the north as it fights for a separate homeland. The 2002 accord helped the South Asian island nation's $27 billion economy post uninterrupted growth and international aid donors have expressed concern at the ending of the truce, saying there can be no military solution to the 25-year conflict. More... Discuss this story Published: Tue Jan 15 21:03:59 EST 2008

As Akashi's three-day visit ended Tuesday, the military announced that 29 Tamil insurgents and three soldiers were killed in worsening fighting in the north. The rebels said 30 soldiers and three Tamil Tigers were killed.

Each side often gives vastly different accounts of the fighting, exaggerating enemy casualties while underreporting its own. Independent confirmation is unavailable since the battle zone is restricted.

Akashi, who has made 15 trips to Sri Lanka - in a vain attempt to end the civil war, said he worried the end of the cease-fire could trigger even more violence and more civilian casualties, ``with dire humanitarian consequences.''

``I conveyed ... the serious concern of the government of Japan on some of the recent moves,'' Akashi said.

He said he also urged Rajapaksa to improve Sri Lanka - 's human rights situation and told the president that only a political agreement could end the conflict between the separatist rebels and the government. Such a solution would require devolving power to local governments, he said.

However, military officials have said they hope to crush the rebels by force by the end of the year.

The Japanese government will closely monitor the situation and will review its financial assistance accordingly, Akashi said.

``Our aid package is based on a complex consideration of factors,'' he said. ``What the government does or does not do will be an important consideration.''

A halt or decrease in aid would be a serious blow to Sri Lanka - , especially with its plan to spend a record 166.4 billion rupees (US$1.5 billion; euro1 billion) on its defense budget this year.

Sri Lankan Foreign Secretary Palitha Kohona gave a different assessment of Akashi's trip, saying the envoy promised Rajapaksa that Japan would continue giving aid.

In their meeting, Rajapaksa explained to Akashi that he pulled out of the cease-fire because the deal had not delivered its promised benefits and the rebels used it as cover to build up their military strength, Kohona said.

The Tamil Tigers have been fighting since 1983 for an independent state for Sri Lanka - 's ethnic Tamil minority after decades of being marginalized by successive Sinhalese-dominated governments. The fighting has killed more than 70,000 people.

Violence continued to rage along the front lines, where government soldiers are facing off against rebel fighters defending their de facto state in parts of the north.

Both sides fought three battles in northeastern Weli-oya region Tuesday afternoon, killing four rebels and a soldier, the military said.

Soldiers pushed into rebel-held territory in northern Mannar district Monday and captured nine Tamil Tiger bunkers, killing nine insurgents, said military spokesman Brig. Udaya Nanayakkara. Two soldiers also died in the fighting, he said.

Six other attacks at different points along the front lines Monday killed at least 16 other rebels, the military said.

The rebel-affiliated Web site TamilNet reported that Tamil Tiger fighters in Mannar held off a major military offensive backed by artillery and airstrikes in a fierce battle that killed at least 30 soldiers and three rebels. The rebel fighters recovered the body of one soldier, but said they saw other bodies across the field of battle, the Web site reported.

Violence has surged since the government announced its withdrawal from the cease-fire Jan. 3.Discuss this story Published: Tue Jan 15 20:49:54 EST 2008