Yemen's Houthi rebels have released a prominent activist nearly six months after detaining him.

International rights groups had appealed for Hisham al-Omeisy's release since he was detained on Aug. 14 in Sanaa, the rebel-held capital. Al-Omeisy's brother, Essam, said he was released Monday and is at home in good health.

A vocal critic of all parties to the devastating civil war, al-Omeisy has used social media to document the conflict and its toll on civilians. He was held without charge in an undisclosed location.

The Houthis, Shiite rebels allied with Iran, have detained scores of activists, journalists and lawyers. Rights groups have documented dozens of cases of forced disappearances and arbitrary arrests, and say detainees have been tortured to death inside Houthi-run facilities.