Cairo (AFP) - Egyptian military prosecutors ordered on Monday the detention of investigative journalist and rights activist Hossam Bahgat on suspicion of publishing false information, the news site for which he works said.

The Mada Masr website said Bahgat, 37, was ordered detained for four days for questioning on suspicion of "spreading false news aimed at harming national interests".

Bahgat was detained overnight after he responded to a military summons over his investigative reporting on a military trial that the army has not officially confirmed or denied.

The New York-based Committee to Protect Journalists called on Egypt to release Bahgat, who was a prominent human rights defender before entering journalism.

"The Egyptian military has already indicated its contempt for the role of an independent media with a series of arrests of journalists. This latest detention is a clear attempt to stifle reporting," the CPJ statement said, quoting its Middle East coordinator Sherif Mansour.

Human Rights Watch describes Bahgat, founder of the Egyptian Initiative for Personal Rights, as "a leading defender of civil rights and liberties in Egypt" who played a prominent role in the 2011 revolution that toppled longtime president Hosni Mubarak.

On Monday, a statement from HRW said: "Military prosecutors should drop the charges and release him immediately."

"Continuing to hold Hossam Bahgat or putting him on trial would be a definitive signal that (President Abdel Fattah) al-Sisi and his government have no interest in rolling back the repression of the past two years," HRW's Middle East Director Sarah Leah Whitson said.