Authorities have informed that a suicide bomb attack Sunday in Afghanistan's southern Zabul province killed at least three people.

CNN has reported that those killed included one of the guards of a private security firm deployed in a market area, said Mohammad Jam Rasool Yar, a spokesman for the governor. The other two killed were reported to be civilians.

It was further revealed by the report that the blast also injured seven people. Other reports gave a higher death toll.

It was also noted by the report that militant violence has escalated in the country's southern region where U. S.-led coalition forces are involved in a campaign to drive out the Taliban.

NATO's counterinsurgency campaign, centered in Helmand province since February, is expected to focus next on Kandahar province beginning in June, the report said. (With Inputs from Agencies)