Yemeni officials say a bomb attack outside a mosque in northwestern Yemen has killed at least 18 people and wounded some 45 others.

Officials say the bomb went off Friday as worshippers, including government soldiers, were leaving a mosque in the Saada region. They say the device was hidden in a vehicle near the entrance of the Bin Salman mosque.

There was no immediate claim of responsibility for the attack.

Shi'ite insurgents have been fighting Yemeni government forces in the Saada region since 2004. The conflict has killed thousands of people.

On Tuesday, rebels in the region killed seven government troops in an ambush.

Some information for this report was provided by AFP, AP and Reuters.