(Updates death count in lead, adds U.S. military sourcing )

BAGHDAD, Feb 18 (Reuters) - At least five Iraqi civilians were killed and 14 wounded when a barrage of rockets hit areas near Baghdad's international airport, including the headquarters of the U.S. military, it said on Monday.

It was one of the deadliest rocket attacks on a residential area of Baghdad in months.

The U.S. military said two of its soldiers were also injured when the rockets struck its sprawling Camp Victory base near Baghdad airport and regions nearby, and that six suspects had been taken in for questioning

Major-General Qassim Moussawi, spokesman for Iraq's military in Baghdad, said the bombs hit an area in the mainly Sunni Khadhra district to the west of the airport in the south of the city.

Police said they were fired from a neighbouring Shi'ite area.

The U.S. military says "special groups", the term it uses to describe rogue elements in the Mehdi Army militia of Shi'ite cleric Moqtada al-Sadr, are now usually responsible for mortar and rocket attacks in Baghdad.

On Sunday, U.S. military spokesman Rear Admiral Gregory Smith said there was evidence that these groups, which Washington says are backed by Iran, were increasingly using secret weapons stores to attack U.S. and Iraqi forces.

Smith said 212 weapons caches had been found in the last week, including two discovered in Baghdad which he said had "growing links to Iranian-backed special groups".

David Satterfield, the U.S. State Department's Iraq coordinator, said last week Iran was "intent on continuing to promote violence within Iraq". Tehran denies such accusations.

Mortar and rocket attacks used to be an almost daily occurrence in the capital as rival Shi'ite and Sunni fighters bombarded each other's communities.

But attacks have fallen dramatically in recent months, mirroring a general fall in violence across Iraq, on the back of a deployment of 30,000 additional U.S. troops.

The Iraqi military said on Saturday attacks in Baghdad had dropped by up to 80 percent thanks to a year-long security crackdown on al Qaeda militants and feuding Sunni Arab and Shi'ite gunmen.

Lieutenant-General Abboud Qanbar, who headed the clampdown, said he hoped the improved security situation might allow for concrete blast walls, erected across the city to deter al Qaeda car bombers, to be taken down "in the coming months".

(Reporting by Michael Holden, editing by Mohammed Abbas and Mary Gabriel)

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