A human rights advocate says Egyptian authorities have released a leading investigative journalist and human rights advocate who had been detained under accusations of spreading "false news."

Heba Morayef, associate director of the Egyptian Initiative for Personal Rights, announced on social media Tuesday the release of Hossam Bahgat, who was detained Sunday after being summoned to an intelligence building in Cairo.

Bahgat is one of Egypt's best-known rights advocates. He founded the group Morayef now works for in 2002, and has been honored with a Human Rights Watch Alison Des Forges Award in 2011.

No further information was available in the immediate moments after Bahgat's release.

The army has said that Bahgat was referred to military trial for "compromising national security" and writing about the military without its written permission.