US Secretary of State Mike Pompeo on Tuesday urged key ally Egypt to respect freedom of the press, days after Egyptian security forces raided the office of independent news outlet Mada Masr and briefly detained staff members.

“As part of our long-standing strategic partnership with Egypt, we continue to raise the fundamental importance of respect for human rights, universal freedoms, and the need for a robust civil society,” Pompeo said in a press conference.

"We call on the Egyptian government to respect freedom of the press and release journalists detained during a raid last weekend," he added.

On Sunday, Mada Masr said plain clothes security forces raided the website's office in Cairo, arresting three staff members including editor-in-chief Lina Attalah, and seizing their phones and laptops. They were all released later in the day.

The incident followed the arrest of one of their editors, Shady Zalat, at his home a day earlier. He had been detained in an unknown location until he was released also on Sunday.

Mada Masr, which publishes critical and investigative reports in Arabic and English, was one of hundreds of news websites blocked by Egyptian authorities two year ago. The website can be accessed locally only through a virtual private network (VPN) app.

Egypt's prosecutors said Monday that investigations by the country's national security apparatus concluded that Mada Masr was founded by the now-banned Muslim Brotherhood group with the aim of spreading false news to disrupt public order.

Last month, the UN human rights office called on Egypt to protect people's rights to freedom of expression and peaceful assembly, after a series of arrests targeting protesters, journalists and human rights advocates in response to rare anti-government demonstrations that took place in September.