The victims were heading home from the hospital after the mother had given birth when the bomb planted by Taliban insurgents tore through their vehicle in Khost province on the Pakistan border, police said.

Roadside bombs are the weapon of choice for the militants who are fighting in an insurgency to bring down the Western-backed government in Kabul.

The deadly improvised explosive devices (IEDs) often miss their military targets and hit civilians who use the same roads.

The United Nations says 1,145 civilians were killed in the war in the first six months of this year, blaming 80 percent of the deaths on insurgents, with more than half caused by roadside bombs.

"Six people, three women, two adult men and a newborn baby were killed," deputy provincial police chief Mohammad Yaqoub told AFP.

Relatives said the family was returning home after the mother delivered her baby in hospital in Sabari town.