A powerful explosion rocked downtown Kabul this evening, the second blast of the day to hit the Afghan capital.

Officials were trying to determine the exact location of the explosion and there were no immediate reports of casualties, Kabul police spokesman Abdul Basir Mujahid said.

An interior ministry spokesman said the blast was caused by a car bomb.

Earlier today, a suicide bomber struck a street leading to Kabul's international airport, but no casualties were reported.

No group immediately claimed responsibility for the bombings. The bombing mark the latest assaults on the war-scarred Afghan capital.

A Taliban suicide car-bomber struck a French restaurant popular with foreigners in Kabul on Friday, killing two people in a New Year's Day attack.