BELGRADE, Serbia (AP) — Dozens of Serbian high school students have staged a sit-down protest demanding that authorities release a fellow student who was jailed during weekend anti-government protests in Serbia.

The students marched Monday from their school in downtown Belgrade toward the main police station in the Serbian capital, where they sat on the ground.

Authorities say they detained 18 people following incidents during demonstrations Saturday and Sunday against Serbia's populist President Aleksandar Vucic.

Protesters on Saturday burst into the state-TV building in Belgrade. More skirmishes with police took place Sunday when protesters surrounded the Serbian presidency during Vucic's press conference.

Protests against Vucic have been going on weekly for three months demanding democratic and media freedoms. Vucic has accused the protesters of violence, saying perpetrators will be punished.