Cairo - Officers from Egypt's domestic intelligence agency searched the home of detained German-Egyptian student activist Philip Rizk in the early hours of Monday, his sister and human rights lawyers lawyers said.

Rizk has been held at an unknown location since late Friday night after he and 14 activists finished a symbolic, 10-kilometre march in Cairo to protest against the blockade of Gaza.

Around a dozen officers from the domestic intelligence State Security Investigation service came to Rizk's family house at around 1.30 am, Rizk's sister Jeannette told Deutsche Presse-Agentur, dpa. Two officers searched the house while the rest surrounded it.

"Around 15 minutes ago, they came to the door and started ringing the doorbell like crazy. We were all sleeping," Rizk's sister told dpa as the officers searched her house. "I am hiding in the bedroom with my mother in the back of the house. My father is out front talking to security."

She said that when asked for a search warrant, the officers replied, "We are State Security. We don't need a warrant."

Human-rights lawyer Gamal Eid, director of the Cairo-based Arabic Network for Human Rights Information, who came to the Rizk's house after the State Security officers arrived, told dpa that the officers wanted Rizk's father to come with them to sign a paper that would allow them to release his son. Eid counseled him not to go.

Both Eid and Jeannette Rizk said that an official from the German Embassy in Cairo was present, but a spokesman for the embassy on Monday said he could not comment on the case.

A friend of Rizk's, speaking to dpa early Monday morning on condition of anonymity, said that family and friends "don't wish to antagonise the government. We're not trying to make any grand statement. We just want Philip released. He's one of the most peaceful people I've met. I'm very worried for him."

Since he was detained last Friday, lawyers, family and friends say they have not had reliable information about where Rizk is being held or on what charges. (dpa)