A British teenager has been arrested over a smartphone video he recorded which showed a military helicopter in the background, his family says.

Muhammed Fathi Abulkasem, 19, from Manchester, was detained shortly after he arrived in the Egyptian city of Alexandria on 21 November.

His cousin, humanitarian relief worker Shareen Nawaz, said the student had been travelling from Libya and filmed the video while his flight was landing, capturing a military helicopter flying by.

"We didn't hear from him until 12 hours later," Ms Nawaz said.

"He basically told us he is held on suspicion of collecting information against the military."

Ms Nawaz told The Associated Press that authorities checked her cousin's phone at the airport.

She claims he had been cautioned by staff at his hotel that his booking appeared "suspicious," without elaborating.

Ms Nawaz added that her cousin had been in court three times over the past week and that a lawyer assigned to his case had quit.

The Foreign Office confirmed a Briton had been arrested in Alexandria, while Egypt's foreign ministry could not immediately be reached for comment.

Taking unauthorised photographs or footage of or near military facilities, equipment or personnel is strictly prohibited in Egypt.

The news comes just days after British academic Matthew Hedges was released from prison in the United Arab Emirates, despite the country claiming he was a member of MI6 and was spying on military systems.