A suicide attacker on foot blew himself up near a NATO convoy in southern Afghanistan on Sunday, seriously wounding three civilians, while a roadside bomb killed a policeman in the east, officials said. The latest violence came a day after the US military announced six of its troops were killed in eastern Nuristan province - the most lethal attack in a year that has been the deadliest for foreign forces since the 2001 invasion. In Helmand province, the suicide bomber detonated himself near the NATO convoy in the town of Gereshk. None of the soldiers were hurt, but three civilian bystanders were critically wounded, said Helmand police chief Mohammad Hussein Andiwal. NATO's International Security Assistance Force did not immediately have information on the attack.