The press accreditations of a number of journalist trying to report on the G20 summit were cancelled Friday "for security reasons", Germany's Federal Criminal Police Office said.
A photographer with the German daily Weser Kurier had his accreditation withdrawn "with no mentioned reason", according to a statement from the paper.
And Junge-Welt reported one of its journalists was also denied entry to the press center at the summit after his accreditation papers were taken from him by the federal office.
German media said several other journalists faced the same fate.
"The Federal Press Office decides on the withdrawal of the accreditation with security authorities", the agency said via Twitter.
The action against the journalist occurs as the leaders of the world's 20 biggest economies meet in Hamburg amid violent clashes between police and demonstrators.
Several hundred protesters, who call themselves the Black Bloc, have since Thursday held "Welcome To Hell" protests in an attempt to disrupt the summit.
At least 196 police officers have been injured in the riots and more than 50 protesters have been arrested.
The Black Bloc blames police for escalating tensions and using what it says are disproportionate measures against demonstrators.
