A U.S. drone strike Monday aiming for an al-Qaida leader has killed five militants in the country’s south as part of a Yemeni offensive against the Islamist group, Yemeni officials said.

They said the airstrike targeted Qaid al-Dahab, a local leader of al-Qaida, in a convoy of three cars near the town of Radda, 160 kilometers (100 miles) south of the capital, Sanaa. Four militants were wounded. The officials said al-Dahab’s fate was not yet known.

Al-Dahab’s sister was the wife of Anwar al-Awlaki, the U.S.-born radical militant cleric killed by a U.S. drone strike last fall.

There was no immediate word from Washington on the strike that targeted al-Dahab.

On Sunday, U.S. Defense Secretary Leon Panetta defended drone strikes in Yemen as a measure “to defend and protect the United States of America.’’ He was interviewed by the American ABC TV network.

Al-Qaida’s branch in Yemen, known as al-Qaida in the Arabian Peninsula, is one of the movement’s most dangerous offshoots. The U.S. considers the impoverished country as a key battleground in the war against al-Qaida.

The terror network has had a presence in Yemen for years, but expanded its influence during last year’s political upheaval when millions of Yemenis rallied across the country demanding the ouster of their longtime ruler, Ali Abdullah Saleh. The militant group seized control of several towns in the south during the turmoil.

Earlier this year, al-Dahab’s brother, Tariq, led militants who stormed and briefly occupied Radda, They pulled out after authorities released 15 of his men from jail. Tariq was later killed in a family feud.