Yemen has asked for US drones to be used "in some cases" to target Al-Qaeda leaders in the country, its foreign minister said on Wednesday.

"Drones were used upon Yemen's request in some cases against fleeing Al-Qaeda leaders," Abu Bakr al-Kurbi said on the sidelines of a counter-piracy conference in Dubai, in a first official Yemeni confirmation.

Yemeni troops have this month recaptured a string of towns which Al-Qaeda militants overran last year across the province of Abyan.

In an interview with ABC television's "This Week," US Defence Secretary Leon Panetta defended in May the use of drones as "the most precise weapons we have" in the campaign against the militant group.

His comments were the first time the US formally acknowledged the use of unmanned drones against Al-Qaeda suspects in Yemen, where such reports had not been confirmed.

"The fear lies in the infiltration of extremists and terrorists into Yemen" from Somalia, said Kurbi. "It is very difficult for us to tell the difference between someone displaced for humanitarian reasons and a terrorist."

In February, the commander of the African Union forces in Mogadishu, Major General Fred Mugisha, said Somalia's Al-Qaeda allied Shebab fighters, close to collapse, were fleeing the war-torn country in large numbers for Yemen.

Earlier this month, a Somali suicide bomber killed the army commander for southern Yemen, General Salem Ali Qoton, who had led a five-week-long offensive against the jihadists.

Last year a record 103,000 refugees, asylum seekers and migrants crossed the Gulf of Aden and Red Sea from the Horn of Africa -- mainly Somalis and Ethiopians.

Kurbi said Al-Qaeda militants had "developed their capabilities to move from one place to another," adding that "it is not unlikely" that jihadists in Yemen might have in turn fled to neighbouring Oman.

Omani media on Tuesday quoted foreign ministry official Saeed Badr bin Hamad al-Busaidi as saying his country was investigating reports that Al-Qaeda militants had infiltrated the Gulf sultanate.

His remarks came after a security official in Sanaa said five Al-Qaeda militants had escaped from a prison in the western Yemeni city of Hudaydah.

Yemen and Oman share a long border through desert and mountainous regions.

On Saturday, the army took control of the southeastern town of Azzan, an Al-Qaeda bastion deserted by the militants a week earlier.

According to several sources, the fighters who fled Azzan, in the southeastern Shabwa province, have sought refuge in an eastern region of Yemen close to the border with Oman.