Overnight drone strikes killed at least 20 suspected Al-Qaeda militants in Yemen, where Washington has conducted a sustained drone war against jihadist leaders, tribal sources and witnesses said on Tuesday.
The twin raids targeted Al-Qaeda positions near Rada, a central town which has been the focus of deadly fighting between the jihadists and advancing Shiite rebels, the sources said.
The United States is the only country operating drones over Yemen, but US officials rarely confirm individual strikes.
Washington regards Al-Qaeda's Yemen branch as its most dangerous and there has been no let-up in the drone war even as the jihadists battle the Shiite rebels alongside Sunni tribes.
The rebels, known as Huthis from the name of their leading family, overran the capital Sanaa in September and have since advanced south from the mainly Shiite northern highlands into Sunni majority areas.
The Rada area is confessionally mixed and has seen deadly clashes in recent weeks.
Armed tribesmen killed 22 rebels in a series of attacks in the area late on Monday, tribal sources said.
The attacks came as a four-day ultimatum expired for the rebels to withdraw, one tribal source told AFP.
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The rebels captured several areas around Rada late last month after a suspected US drone strike and raids by the Yemeni air force killed dozens of Al-Qaeda militants and their Sunni tribal allies.
The Huthis have seized on chronic instability in Yemen since the 2012 ouster of veteran strongman Ali Abdullah Saleh to take control of large parts of the country.
The fighting has raised fears that Yemen -- which neighbours oil kingpin Saudi Arabia and lies on the key shipping route from the Suez Canal to the Gulf -- may collapse into a failed state.
The rebels took the Red Sea port of Hudeida last month and the army deployed hundreds of allied militiamen in the southern city of Aden on Tuesday to thwart any move by either the rebels or Al-Qaeda to seize the country's most important port and oil refining centre.
"We came to Aden to protect security and military institutions as well as vital installations, in coordination with the leadership of the fourth military region," militia commander Abdullatif al-Sayed told AFP.
"We will confront any armed group attempting to undermine security and stability in Aden, whether the Huthis or Al-Qaeda," he added.
Sayed was speaking after talks with General Mahmoud al-Subaihi, commander of the fourth military region, which includes Yemen's third largest city Taez, as well as second city Aden.
The Shiite rebels did not enter mainly Sunni Taez after a deal was reached between the provincial authorities and rebel representatives to avoid any fighting in the city of nearly 500,000 people.