Egypt arrested four employees of Turkish state news agency Anadolu on Wednesday after a raid on its Cairo office at a time of rising tensions between the regional rivals, the agency said.
Following the raid on Tuesday, Egyptian police searched the Cairo office through the night before formally arresting four employees: one Turk and three Egyptians.
The Turk, Hilmi Balci, was in charge of finance and administrative duties for the office.
Turkey summoned Egypt's charge d'affaires on Wednesday to protest the raid.
"This is an act of harassment and intimidation against the Turkish press and we strongly condemn it," Turkey's foreign ministry said in a statement.
"We expect Egyptian authorities to immediately release (Anadolu's) employees," it added.
The Turkish and Egyptian governments are fierce rivals, since Ankara strongly supported Egypt's Muslim Brotherhood administration that was overthrown by a military coup in 2013.
They are on opposing sides of the Libyan conflict, where Turkey supports the government in Tripoli, which is under siege from military general Khalifa Haftar, who is supported by Egypt and the United Arab Emirates.
Anadolu said police stormed its office on Tuesday evening, turning off surveillance cameras and cutting the internet. It said its arrested employees were refused access to their lawyer.
"This hostile step taken by the putschist Egyptian authorities against Anadolu Agency staff members is a sign of their helplessness," said Fahrettin Altun, spokesman for the Turkish presidency.
The United States, an ally of both countries, said it had seen reports of the episode.
"If true, we call on the Egyptian government to release the detained journalists and allow for a free and open press in Egypt," a State Department spokesperson said.
The United States has strong ties with Egypt's general turned President Abdel Fattah al-Sisi, seeing him as an ally against political Islam, despite concern on his human rights record.