Two U.S. drone strikes Wednesday killed at least four suspected al-Qaida militants and destroyed the house of another in a mountainous area south of the capital, Sanaa, a Yemeni security official and witnesses said.

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

The second strike targeted the house of a suspected jihadi, Hamed Radman, believed to be al-Qaida member, the official said. He said it was not known whether Radman was inside the house at the time.

A witness in a nearby village said he saw columns of smoke rising into the sky after two explosions rocked the area. He said that U.S. drones have been flying over his village for three days and are still in the sky.

The region, shaped like a triangle and located in the middle of three provinces of central Damar, southern Ibb and eastern Hodeida, 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.

In Sanaa, Yemeni authorities have raided houses of suspected al-Qaida members in the past 48 hours, arresting more than 15, including a man whose brother was killed in one of the drone strikes in southern city of Abyan the past months, official said.

The arrests are part of tightening security measures in Sanaa in the vicinity of the foreign embassies, companies and hotels.

Yemen's al-Qaida branch, known as al-Qaida in the Arabian Peninsula, is considered the group's most dangerous.