Reporters Without Borders said it was outraged by a violent crackdown in Belarus in the run-up to presidential elections, due in less than three weeks.
Police in plain clothes beat up at least nine journalists who covered the arrest of main opposition candidate, Aleksandr Kozulin in the capital Minsk on 2 March. Opposition activists were also arrested.
"These incidents are unacceptable and fuel fears of a presidential election in a climate of terror, without a shred of freedom or democracy", said Reporters Without Borders. "The international community should react to ensure that the poll is not marred by further brutality against the press and opposition,"
Plain clothes police arrived in a bus to disperse the crowd as demonstrators and journalists gathered in front of the police station in Kastrychnitsky where Kozulin was being held.
Several agents seized Oleg Ulevich (photo), Russian correspondent for Komsomolskaya Pravda v Belorussii, while he was taking photos of the arrests of activists in front the of the police station.
They threw him to the ground and kicked him where he lay. He was then taken to the Leninsky police station with a broken nose and numerous bruises to his face. He is currently in No. 9 hospital and is expected to stay there for at least four days for observation.
Yulia Darashevich, Aleksandr Grits and Vasily Fedosenko, respectively photographers for the weekly Nasha Niva and news agencies AP and Reuters, were detained and then released after police examined the pictures they tried to take during the arrest.
Andrey Maksimov, journalist for Aleksandr Kozulin's press service and Dzmitry Brushko, journalist on weekly Belgazeta, were both also arrested for several hours.
Plain clothes police tried to snatch a camera from a journalist working for the ByMedia.net agency before colleagues came to help.
Sergei Pulsha, correspondent for BelaPAN agency was struck in the face by a police officer.
Finally, Dmitry Madorsky, cameraman for Reuters, was also kicked and struck in the face and was taken to the city's hospital no 10.
In another incident, three Ukrainian journalists of TV channels 1+1, Tonis and 5Kanal were refused entry to Belarus after arriving at the airport in Minsk. They had come to cover a demonstration in support of one of the opposition candidates, Aleksandr Milenkevich.