Omani and Yemeni security forces are hunting for several Al Qaida members fleeing a US-backed military offensive in southern Yemen who have crossed into Oman, a senior Yemeni security source said on Tuesday.

The infiltration into Oman, which sits on one side of the Strait of Hormuz, the conduit for a third of the world’s seaborne oil exports, raises concern that Islamist militants may try to set up a base in a region of strategic importance for the United States.

“A limited number of Al Qaida elements managed to cross the border line to Oman in recent days,” the Yemeni source told Reuters. “Both sides are coordinating at the level of the border guards and the intelligence service to pursue and capture them.” He declined to give further details.

An Omani foreign ministry official, Badr Bin Hamad Al Busaidi, told the newspaper “Oman” that his country was hunting infiltrators from Yemen but said no arrests had been made and declined to give any further information.

The small oil and gas exporter is an ally of the United States and Britain.

Saudi Arabia fought a militant insurgency from 2003 to 2006 in which Al Qaida members killed dozens of people in attacks on foreign workers and on government facilities.

Many of the militants fled the Saudi crackdown and regrouped to set up a base in Yemen. Ansar Al Sharia, an offshoot of Al Qaida, last year exploited political turmoil to capture several cities in southern Yemen, before being driven out this month.

Yemeni officials have said some of its fighters have fled toward a province bordering Oman.

The sultanate was rocked last year by mass protests against corruption and unemployment triggered by the Arab Spring uprisings.

These protests have now largely given way to sporadic labour protests in the oil, health and education sectors.