Two British servicemen have been detained in Iraq amid allegations they fired on police in Basra.
A senior Iraqi official said British military sources had told him the men were undercover soldiers in civilian clothes.
The official said: "They were driving a civilian car and were dressed in civilian clothes when a shooting took place between them and Iraqi patrols.
It is understood the men were arrested following clashes between British soldiers and protesters, during which two tanks were set on fire.
Witnesses said demonstrators had thrown stones at the British tanks and troops fired warning shots back.
Soldiers then jumped from the vehicles when they were set on fire and withdrew without any further shots being fired.
A Ministry of Defence spokesman said: "We can confirm that two military personnel were detained by Iraqi authorities earlier today."
The spokesman refused to comment on reports the men were working undercover and said the exact reason for their detention was not yet known, Sky News reports.
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