An Isle of Wight man is among hundreds of activists from the Gaza-bound aid flotilla intercepted by Israeli forces who have arrived in Turkey.
Peter Venner, from Ryde, was on the Mavi Marmara which was carrying aid supplies when it was boarded by armed commandos overnight on Sunday.
Turkish planes carrying the activists arrived in Istanbul from Israel. Nine people died in the raid.
Mr Venner's partner Rachel Bridgeland said she hoped he would be home soon.
She said: "It's absolutely terrible not knowing what has happened to him and it's terrible that the British government hasn't done more, but they don't want to fall out with Israel.
Tonnes of aid
"They should insist that the British people are allowed to phone us, they have done nothing illegal."
The Foreign Office said that British consular officials in Israel had made contact with all the 36 British nationals held in detention, including Mr Venner.
A spokesperson said it had been in constant contact with the Israeli authorities about their situation.
The six-ship flotilla, carrying 10,000 tonnes of aid, left the coast of Cyprus on Sunday and had been due to arrive in Gaza on Monday.