The US military and spy agencies have stepped up intelligence gathering using surveillance aircraft, satellites and signals intercepts to track al Qaeda targets in and around their base in Yemen, US officials said.

Some of the intelligence is being shared with Yemeni security forces to facilitate their strikes against Al Qaeda in the Arabian Peninsula (AQAP), but could also underpin covert US operations against the group and its leaders, the officials said on condition of anonymity.

"There is a tremendous amount of focus on that country," a US intelligence official said.

An air strike in Yemen on Tuesday has fueled speculation that the US military or CIA have started using unmanned aerial drones to carry out attacks in Yemen. A Yemeni provincial official said the air strike targeted al Qaeda but killed a mediator instead.

Asked about the strike, US officials said Washington continues to play a supporting role by helping Yemeni forces track and pinpoint targets -- suggesting Tuesday's strike was not carried out by a US-controlled drone.

"We continue to support the Yemenis as they go after this threat inside their border," a US military official said.

But another US official acknowledged there was an increasingly "fine line" between playing a supportive role and taking the lead.

AQAP and one of its leading figures -- American-born Muslim cleric Anwar al-Awlaki -- have become high priority US targets since the group took responsibility for a failed plot to blow up a US passenger jet on Christmas Day.

Awlaki has also been tied to an Army psychiatrist charged with killing 13 soldiers in a November 2009 shooting rampage at Fort Hood, Texas.

The intelligence gathering effort expanded in the wake of a secret order issued last September by General David Petraeus, who heads the US military's Central Command.

Central Command, which oversees US wars in Iraq and Afghanistan, has been positioning Reaper drones at a base in the Horn of Africa, officials said last week.

Washington has sought to play down any direct US role in strikes in Yemen, wary of stoking anti-American sentiment and broadening al Qaeda's appeal.

But the Pentagon has made little secret about expanded US assistance to Yemeni security forces.

Under a $155.3 million security package for Yemen announced earlier this year, the Pentagon has earmarked $34.5 million to expand the capabilities of Yemen's Special Operations Forces to conduct counterterrorism operations.

The rest of the money will be used to upgrade Yemen's fleet of helicopters and fixed-wing aircraft. – Reuters