Khost : Hours after the attack, a suicide bomber in a separate part of Khost blew himself up at the gate of an Afghan road construction firm, killing a guard and wounding six other people, another official said.

In the southeast, the defence ministry has launched an operation involving about 1,700 personnel to wipe out insurgents from four southeastern provinces, the defence ministry said, adding the operation was backed by US-led troops. Separately, the ministry said, foreign and Afghan militants were planning to blow up a major water dam that provides power for the capital, Kabul. Based on intelligence reports, it said the insurgents were aiming to target the country's infrastructure.

Also on Saturday, Afghan troops killed three Taliban rebels in an engagement in southern Helmand, the defence ministry said.