Dozens of Saudi Islamist militants have left the battlefields of Syria and Iraq for Yemen, where their experience appears to have contributed to a spate of lethal al Qaeda attacks, a senior Yemeni security official said.

The influx detected in the last few months is worrying for Yemen, a turbulent country where several hundred Saudi militants are already thought to be fighting alongside their Yemeni counterparts in al Qaeda in the Arabian Peninsula (AQAP).

The initial core of Saudis fled to Yemen after the kingdom defeated a violent al Qaeda campaign between 2003 and 2006, helping to create AQAP with their Yemeni comrades in 2009.