The British Foreign Office said on Tuesday that some 40 Britons were believed to have been detained by Israel after its raid on a convoy carrying aid to Gaza.
The Foreign Office confirmed that one Briton had been injured and British officials are trying to know the exact number of the detained Britons.
At least 10 civilians were killed and some 30 others injured on Monday during an Israeli military raid against the flotilla carrying aid to the besieged Gaza Strip. The ship was carrying more than 700 people.
Prime Minister David Cameron described Israel's deadly assault as "unacceptable" and called for a "constructive" response to legitimate criticism of its actions.