Updated

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.

Later Monday, Yemen officials said seven other al-Qaida militants were killed in southern Yemen, but they disagreed over how they died. Security officials said they were killed in an airstrike, but the military said they were hit by a missile fired from a ship off Yemen's shore. Local tribal officials said the seven militants were in two cars.

Yemen's army is pushing an offensive to uproot al-Qaida-linked militants from their strongholds in the south. The U.S. is aiding the operations. Panetta said its activities "don't necessarily involve boots on the ground," according to a transcript of the interview on the ABC website.

In their offensive, Yemeni government troops have retaken most of a southern provincial capital from al-Qaida fighters.

The officials said Monday that the army holds 90 percent of Zinjibar, the capital of Abyan province, which fell to al-Qaida last year. They say 48 hours of fierce fighting left 22 militants and nine soldiers dead.

They said the army was advancing toward Jaar, another town in militant hands for over a year, in a three-pronged attack supported by heavy artillery shelling and air raids.

The officials spoke on condition of anonymity in line with military regulations.