At least five people were killed and 50 others were injured, when a powerful bomb ripped apart a private omnibus at Nittambuwa near Colombo on Friday.
The bus, packed with passengers, was on its way from Kandy to Colombo, a security official told Hindustan Times.
The police suspected the hand of the LTTE in the blast.
An observer of the Sri Lankan security situation said that the incident indicated that the LTTE had begun to take soft targets outside the highly guarded capital city of Colombo.