Philip Rizk at the pro-Gaza rally before his detention
Egyptian police have released a pro-Palestinian blogger who was detained last week during a rally.
Egyptian-German student Philip Rizk was held on Friday, north of Cairo, where he helped organise a protest in support of the Gaza Strip.
Eyewitnesses said he was bundled into a white van with no licence plates, which then sped off.
Ritz says he was "terrified" but not abused physically, according to a local human rights group.
A security official confirmed the release and said an inquiry was ongoing into Mr Rizk's activities.
Mr Rizk, who lived in Gaza for two years, writes the blog Tabula Gaza, and has just completed a short documentary about non-violent protest against Israeli operations in the Gaza Strip.
"I was repeatedly questioned about everything and I was terrified," Mr Rizk said, according to a statement from The Arabic Network for Human Rights Information (ANHRI) in Cairo.
"Although I was not abused physically, I was blind-folded all the time," he added.
Egyptian officers also threatened the graduate student from the American University in Cairo with long-term imprisonment. They asked if he supported Hamas, worked for Israel, or was a Christian evangelist, the group says.
Early on Monday, plain clothed security officials searched the Rizk family home and threatened to detain his father, but were dissuaded by the presence of a human rights lawyer and an official from the German embassy, family members say.
Mr Rizk also had personal belongings seized, including digital cameras, a video camera, a mobile phone, an iPod, and a number of books, according to ANHRI. The password to his personal email and his blog was also gained.
Meanwhile, a second Egyptian blogger remains in detention, security officials said; Diaeddin Gad, 22, was also detained on Friday after criticising Egyptian government policies, especially in relation to Israel's recent military offensive in Gaza.
Many Arabs have criticised Egypt, which has the only border crossing with the Gaza Strip to bypass Israel, for not fully opening the frontier to aid and the wounded during the recent conflict in Gaza.