A Briton detained in Gaza was identified by the British consulate in Jerusalem today.
Officials named him as freelance journalist Paul Martin and said they understood he was also a documentary film-maker.
A spokeswoman for the consulate said the British Government was "very concerned" and had been in touch with Martin's family.
A Palestinian militant group said Martin was arrested yesterday at a Gaza courthouse where he had gone to show support for a militant accused of collaborating with Israel.
The spokesman said Martin was ordered to be held for two weeks.
Hamas police spokesman Ehab Ghussein identified the man as a journalist and said he was suspected of endangering state security.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies