HAVANA (CNN) -- The defamation trial of an independent journalist set
                  off an unusual street disturbance Friday between Cuban dissidents and
                  government supporters.

                  The 20-minute demonstration was one of the most public outbursts in the
                  Cuban capital since rioting near Havana's Malecon waterfront in 1994.

                  A crowd of dissidents had gathered outside the courthouse to support Mario
                  Viera, head of the small and unauthorized Cuba Verdad press agency, who
                  was to go on trial Friday on charges of slandering a government official.

                  "Long live Mario, who defends freedom!" yelled one of Viera's supporters.

                  Pro-government demonstrators immediately responded with chants of their
                  own.

                  "Long live Fidel! Long live socialism!" cried one government supporter.

                  The two sides screamed differing versions of Cuba's national anthem at each other,
                  then exchanged insults.

                  "We Cubans are free in this country! Long live the Revolution! Down with
                  the worms!" yelled government supporter Marta Ofelia Cuallo.

                  Witnesses said another pro-government protester shoved an elderly Viera
                  sympathizer to the ground, ripping a flag from her hands. They said the man
                  also attacked another dissident and chased him down the street, where
                  police kicked and arrested the dissident.

                  Reporters said at least four other opposition members were also detained by
                  police. Two women being taken away in police cars held up and grabbed
                  their wrists before photographers, simulating handcuffs.

                  No government supporters were seen arrested.

                  "We will not allow ourselves to be belittled by these provocateurs, because
                  this is our country," a government supporter said. "It belongs to the Cuban
                  people, to the revolutionaries, to really honest people"

                  Viera had been charged with defaming Foreign Ministry official Jose
                  Dionisio Peraza in an article posted on the Internet. In the article, Viera
                  ridiculed comments by Peraza supporting the establishment of an
                  independent, international criminal court.

                  Viera wrote that Cuban courts "are neither independent nor impartial."

                  If convicted, he could be sentenced to one year in prison, with an additional
                  six months if he refuses to retract his statement, Viera said.

                  Cuba's Foreign Ministry has distanced itself from the case, calling it a private
                  matter between Peraza and Viera.

                  Government critics say the police response proves the government is taking
                  sides.

                  "We believe that if we want to show our support for Mario in a peaceful
                  fashion, we have just as much right to express ourselves as those who toe
                  the official line," a dissident told CNN.

                  After the disturbance, the court suspended Viera's trial. No date has been
                  set for it to resume.

                     Havana Bureau Chief Lucia Newman, The Associated Press and
                                 Reuters contributed to this report.