Monday, June 26, 2006 Posted: 0627 GMT (1427 HKT)
The sources said the attack has all the hallmarks of the Tamil Tiger rebels, but there has been no claim of responsibility.
Maj. Gen. Parami Kulatunga -- who died after he was taken to a hospital -- was the army's deputy chief of staff, the third highest ranking official in Sri Lanka's army.
Two of his military escorts and a bystander were also killed, the sources said.
The suicide bomber rammed his motorcycle into the army vehicle carrying Kulatunga and detonated, the sources said.
Several vehicles were torched in the explosion, and bystanders helped douse the fires.
The attack happened in Panagoda, a southern suburb of Colombo, around 7:45 a.m. (0215 GMT Monday).
Kulatunga was driving to army headquarters from a garrison in Panagoda, where he lived.
Rebel attacks and government reprisals against Tamil strongholds have been frequent over the past few months, in violation of a cease-fire brokered by Norway in 2002.
On April 25, a suicide bomber infiltrated Sri Lanka's army headquarters in an attempt to kill army commander, Lt. Gen. Sarath Fonseka, who was seriously wounded in the attack, blamed on Tamil Tigers.