Beirut: A well-known Egyptian blogger and human rights advocate was briefly detained by Lebanese authorities on Wednesday, according to his lawyer and sister, but it was unclear why.

Sara Tarek, Abdul-Rahman Tarek's sister, was the first to report the arrest of the man also known as Moka. She announced on her Facebook page that her brother was taken into custody from his flat by plainclothes officers on Wednesday in the late afternoon.

She demanded his release, noting that he had spent the previous year in freedom after serving seven years in prison in Egypt.

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After spending about five hours at the police intelligence headquarters in Beirut, Tarek was eventually released by his attorney, Farouk Moghrabi. According to Moghrabi, the reason for the arrest was not immediately apparent.

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Later, Sara Tarek reported that her brother had been released and was now at home. Tarek's arrest and subsequent release were not immediately confirmed by security personnel.

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The UN's independent expert on human rights defenders, Mary Lawlor, tweeted: "I hear extremely disturbing news" that an Egyptian rights advocate living in exile in Lebanon was detained today "without a warrant." In her tweet, she included the foreign ministry of Lebanon.

Following Tarek's release, a group of Lebanese activists decided not to hold the demonstration they had planned outside the police department.