Huseyin Celil, a Canadian citizen, was detained by Uzbek authorities in Tashkent in March and later deported to China.
Beijing accuses Celil of involvement in an attack six years ago on a state delegation in China's western Xingijang Province, the home of Turkic-speaking Uyghurs.
The demonstrators handed over a petition to a Chinese Embassy official and dispersed peacefully after about one hour.
RFE/RL Central Asia Report
SUBSCRIBE For regular news and analysis on all five Central Asian countries by e-mail, subscribe to "RFE/RL Central Asia Report."