A Yemeni security official and witnesses say a U.S. drone strike killed at least four suspected al-Qaida militants in mountainous area south of the capital, Sanaa.

The four were killed while riding a vehicle in the desert area of Oussab al-Ali, about 140 kilometers (90 miles) south of Sanaa, the official said.

The region has become a hideout for al-Qaida militants since the Yemeni government intensified its offensive against their former strongholds in the south over the past several months.

The official spoke on condition of anonymity because he was not authorized to speak to reporters.

A witness in a nearby village said he saw columns of smoke rising into the sky after two explosions rocked the area on Wednesday.