An Egyptian researcher and freelance journalist detained upon his return to Egypt is being investigated for spreading false news, in what his lawyers say is the latest crackdown on press freedoms in the country.

After more than eight hours of questioning in Cairo on Tuesday, prosecutors ordered Ismail Alexandrani to be jailed for 15 days pending investigations, his lawyers from the Egyptian Centre for Economic and Social Rights said in a statement.

Alexandrani is accused of joining an illegal organisation, campaigning for that organisation and spreading false news with the intent of disturbing the public peace and spreading horror among people, his lawyers said in the statement that did not identify the organisation in question.

A police official, speaking anonymously because he was not authorised to brief reporters, said the Egyptian embassy in Berlin had notified airport authorities when Ismail Alexandrani arrived in the country on Sunday.

Alexandrani’s lawyers and his wife, Khadeega Ga’far, said they were told his arrest was due to a complaint filed by the embassy in Berlin. Egypt’s foreign ministry spokesman, Ahmed Abouzeid, denied Egypt’s diplomatic missions abroad had anything to do with the case.

Journalist Abdelrahman Ayyash said on his Facebook page that Alexandrani, an expert on militants operating in Egypt’s northern Sinai peninsula, recently gave a presentation in Berlin on the subject.

The Egyptian government has been battling a long-running insurgency in the region, which escalated after the military ousted the Islamist president, Mohamed Morsi, in July 2013 amid massive protests against his rule.

A crackdown launched after Morsi’s overthrow initially focused on his Islamist supporters but was soon broadened to other dissidents, including secular activists who led the 2011 uprising that ousted longtime leader Hosni Mubarak.