At least 12 civilians were killed in two roadside bomb explosions in Afghanistan on Sunday, officials said.Ten civilians died and at least seven were wounded after their van was hit by a roadside bomb in Tabag district in the country's northeast, Khaama press quoted a police officer as saying.The attack took place in an area where Taliban insurgents routinely attack security forces.In the northern province of Kunduz, two civilians were killed when a roadside bomb struck a passing police vehicle, said Sayed Sarwar Hussaini, a police officer.Four civilians and two policemen were also wounded in the blast.