A powerful mine blast ripped through a bus packed with commuters and schoolchildren in northern Sri Lanka on Thursday, killing at least 62 people, the army said, blaming the Tamil Tiger rebels. The insurgents denied any role in the attack. The explosion, described as "huge" by military spokesman Brig. Prasad Samarasinghe, was the worst single act of violence since the government and Tamil Tiger rebels signed a cease-fire in 2002, and renewed fears of a return to war. A senior rebel leader countered allegations that the Tigers were behind the blast, suggesting the attack could be "the work of forces seeking to create ethnic tension between the Sinhalese and the Tamil population." The Liberation Tigers of Tamil Eelam fought for 20 years to carve out a separate homeland in Sri Lanka's north and east for the country's 3.2 million minority Tamils, who are largely Hindu. The majority of Sri Lankans are Sinhalese, most of whom are Buddhists. A 2002 cease-fire ended large-scale fighting, but violence has persisted, intensifying in recent months, including rebel attacks on civilians. But Thursday's violence dwarfed recent attacks, and a doctor at the hospital where the victims bodies were taken, S. B. Bothota, said that 15 school children were among the 62 killed. Another 78 people were wounded by the blast, which also hit bystanders in a crowded part of Kabithigollewa, a town in the northern Anuradhapura district, a predominately Sinhalese area that is also home to sizable Tamil and Muslim communities. Most of those killed and wounded in the blast were Sinhalese, said a police officer at the scene, who spoke on the condition of anonymity because he was not authorized to speak to the press. Kabithigollewa is near the northeastern districts of Vavuniya and Trincomalee, flashpoints for violence in recent months between the Tamil Tigers and the Sri Lankan military.