Opposition protesters are girding for more demonstrations in Serbia, targeting President Aleksandr Vucic whom they accuse of stifling media freedoms and suppressing the opposition.
The January 11 action is the latest in a series of protests against Vucic.
The demonstrations were triggered last month when thugs beat up opposition politician Borko Stefanovic.
Last week, an estimated 15,000 protesters marched in Belgrade, chanting "Vucic, thief!" and waving banners that read "Stop the Treason, Defend the Constitution and Back the People."
For many protesters, the assault on Stefanovic echoed attacks on political opponents in the 1990s under the rule of late Serbian leader Slobodan Milosevic.
An umbrella group of opposition parties called the Alliance for Serbia blamed Vucic's Serbian Progressive Party for the attack on Stefanovic.
Authorities denied involvement.
A former nationalist, Vucic now is guiding Serbia toward membership in the European Union. He has also sought to maintain ties with traditional ally Russia and to develop relations with China.
The European Commission last year raised concerns about media freedoms in Serbia, denouncing threats, intimidation and violence against journalists.