RFE/RL's Belarus Service reports that police officers detained the 50 people present, including the actors, directors, five theater professionals from France and the Netherlands, and several children.
The detainees were released four hours later.
The incident is the first reported case in Belarus of police breaking up a theater performance.
The play was staged by the Free Theater, an unregistered theater company that is banned from performing in Belarus. The troupe doesn't have its own premises and screens spectators before every performance.
Mikalay Khalezin, the co-founder of Free Theater, told RFE/RL's Belarus Service that the incident reminds him of a poem by Soviet poet Vladimir Mayakosvky in which a sailor storms the Winter Palace during the 1917 Bolshevik Revolution to arrest the temporary government.
"There was a pause of about 20 seconds," Khalezin said. "Then a man with a short haircut walked onto the makeshift scene, stumbling, and asked, "What's going on here?' He reminded me of a sailor during the revolution, saying: 'Who's temporary here? Get out! Your time is up.'"
Khalezin said the French Foreign Ministry has been informed of the incident, as have British playwright Tom Stoppard and rock star Mick Jagger.
Stoppard, Jagger, and British playwright and Nobel Prize laureate Harold Pinter are among the many cultural luminaries to have thrown their weight behind the Free Theater. Stoppard had planned to attend the August 22 performance but canceled his visit at the last minute.
The Free Theater was performing "Eleven Vests," a play by British playwright Edward Bond about violence.