Prison authorities released Alexander Milinkevich several hours early Friday, through a back door at the prison. He later returned to address about 100 supporters gathered outside the jail, despite police warnings that the meeting was unauthorized.

Milinkevich and several associates were arrested last month after a rally in Minsk marking the 20th anniversary of the Chernobyl nuclear disaster.

Milinkevich was the leading vote-getter among opposition candidates in the March presidential election. He finished a distant second behind President Alexander Lukashenko in balloting international observers say was marred by fraud.

Meanwhile, a Minsk court has dropped charges against Stanislav Shushkevich, another opposition figure who faced similar charges in connection with a May Day rally.