Egyptian authorities free Egyptian-German activist

CAIRO (Reuters) - Egyptian authorities have released an Egyptian-German activist and blogger on Gaza, his sister said on Wednesday.

Philip Rizk, 26, was released late on Tuesday. He had been detained by police on Friday night while returning to Cairo from a march in solidarity with the Palestinians of Gaza in Qalyoubia, north of the capital.

His sister did not give any further details about the release, which was also confirmed by one diplomatic source.

Human rights groups had expressed concern at the detention of Rizk, who they said was believed to have been held by state security.

"Detainees held by the SSI (state security) are at risk of torture and other ill-treatment, especially when they are held incommunicado and at undisclosed locations," Amnesty International said in a statement issued before news of Rizk's release.

Police officials were not immediately available for comment.

Early on Monday, plainclothed 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 said.

Rizk recently spent two years in Gaza and had made a documentary about the ordinary lives of Palestinians in the impoverished Gaza Strip.

The Egyptian government is wary that public support for Gaza will boost the popularity of the Muslim Brotherhood, the strongest opposition group in the country, which has ideological and historical ties with Palestinian Islamist group Hamas.

The Egyptian government contributes to the blockade of Gaza by refusing to open the Rafah crossing point without Israeli approval.