Britain has called on Israel to mount a "transparent and thorough" investigation into the killing of nine civilians during the storming of an aid flotilla heading for the Gaza Strip.

Foreign Secretary William Hague said 31 British nationals and a further 11 with dual nationality are now known to have been detained following the seizure of the vessels as they attempted to breach the Israeli blockade of the territory.

He said one individual had already been deported while the rest were being seen by British consular officials.

"They are all in the process of being visited and Israel is giving us the appropriate consular access as, of course, they should," he said.

Mr Hague welcomed a statement by the United Nations Security Council calling for a "prompt, impartial, credible and transparent" investigation into the seizure of the flotilla by Israeli commandos early on Monday.

"We look to Israel to co-operate to implement that resolution with a transparent and thorough investigation," he said.