ADEN/SANAA (Reuters) - An air strike on an al Qaeda position in southern Yemen Sunday killed two top militants planning attacks, a Yemeni security official said.
"The raids ... killed two leading al Qaeda elements who were planning terrorist operations against vital installations in Yemen," the official said in a statement.
Residents earlier told Reuters that up to 20 people may have been killed in the raid in southern Abyan province.
Yemen has boosted security at oil and gas facilities after it declared open war on al Qaeda following the failed bombing of a U.S.-bound plane on Christmas Day which was claimed by the group's regional wing in December.
Western allies and neighboring Saudi Arabia, the world's top oil exporter, fear al Qaeda is exploiting instability in impoverished Yemen to recruit and train militants for attacks in the region and beyond.
"This area (in Abyan) had seen an appreciable rise in activity by al Qaeda elements, which was being monitored by security services," the website of the ruling party said.
Yemen has repeatedly bombed suspected al Qaeda sites, but residents and opposition groups have said dozens of civilians, including women and children, were killed in a December 17 strike in which authorities said more than 30 al Qaeda members died.
Earlier in March, the government expressed regret over the civilian deaths in that raid in south Yemen and said it would pay compensation to families of civilian victims.
Al Qaeda's wing in Yemen has said the attempted Christmas Day attack was in retaliation for the December 17 raid which it accused the U.S. air force of carrying out.
Separately, the group said in an Internet statement that a Saudi militant -- who it said had been active in raising funds in Saudi Arabia for fighters in Yemen, Iraq and Afghanistan -- was killed in a clash with government forces in southern Yemen.
In addition to its conflict with al Qaeda and southern separatists, Yemen is trying to bring an end to a northern Shi'ite insurgency that in November drew in Saudi Arabia. It sealed a truce with northern Shi'ite rebels last month.
The rebels said Sunday they had completed their withdrawal from three districts near the border with Saudi Arabia, Al Arabiya television reported.
A rebel spokesman said the insurgents had handed back state and military buildings to authorities, but warned the military to stay out of villages which had been rebel strongholds during the fighting, the news channel said.
While insurgent violence in north Yemen has faded, tension has escalated with separatists in the south despite an offer of talks by Sanaa, which faces international pressure to quell domestic unrest and focus on a bigger global threat: al Qaeda.
State media said a gang leader driving a stolen car was killed Saturday in a clash in Abyan. A southern opposition news website said the man was a separatist, and that he was shot after he resisted arrest at a checkpoint.
State media also reported that in southeastern Hadramout province a court began the trial of 11 suspected separatists on Sunday on charges including "threatening Yemen's unity."
North and South Yemen united in 1990, but many in the south -- home to most of Yemen's oil industry -- complain northerners have seized resources and discriminate against them.
Additional reporting by Mohammed Ghobari in Sanaa; Writing by Cynthia Johnston and Firouz Sedarat; Editing by Louise Ireland