Yoqubov's daughter Nargiza Yoqubova tells RFE/RL's Uzbek Service that her father was summoned by police in the central Uzbek city of Jizzakh for questioning on July 15, but that he refused to go, fearing possible arrest.
The next day, Yoqubova says she received a phone call from her father, who told her he was in his Tashkent apartment and that police had arrived to detain him.
Yoqubova said the family has "no information about his whereabouts" and is "very worried."
Dozens of human rights activists have been targeted as Uzbek authorities continue a crackdown on dissent. Many have been imprisoned in recent months.