20 killed in attack on Afghan President's running mate

At least 20 people have been killed and 50 injured in a bomb attack in the Afghan capital Kabul.

The explosion was followed by a gun battle near the office of Vice Presidential candidate Amrullah Saleh, who was wounded in the incident.

Three attackers were killed and about 40 civilians were rescued by security forces.

No group has claimed responsibility for the attack.

The violence came on the first day of campaigning for the country's presidential election on September 28.