BELGRADE, Serbia (AP) — Independent Serbian journalists marked on Tuesday the 24th anniversary of the killing of a prominent editor and newspaper publisher who was fiercely critical of the government in Belgrade.

Slavko Curuvija was shot dead at the entrance to his Belgrade apartment during the 1999 NATO bombing of Serbia over its crackdown against Kosovo Albanian separatists.

His killing became a symbol of the struggle for a free press in the Balkan nation.

Independent media organizations, both local and international, warn that critical journalists still face threats because of their work. The government of populist President Aleksandar Vucic – who was information minister at the time of Curuvija's death – maintains tight control over mainstream media outlets.

Four state security officials were charged with planning and carrying out the killing, but no final verdict has been reached despite several retrials and appeals.

Foreign rights groups attended the gatherings of independent journalists on Tuesday to mark Curuvija’s killing.

‘’Our visit comes amidst a spate of recent death threats and pressure, which reflect a wider toxic climate for independent and investigative journalism,’’ said the Media Freedom Rapid Response group.

‘’It is alarming that leading journalists are still receiving death threats and being branded with the same dangerous labels of 'traitors' and 'foreign mercenaries' that were used to lay the groundwork for Curuvija’s assassination,’’ the group said in a statement.

Curuvija was regarded as an enemy of the state by the regime of former Serbian President Slobodan Milosevic. The state-run media controlled by Milosevic’s family accused him of ‘’inviting’’ NATO to bomb Serbia. The NATO intervention in Serbia was in response to Milosevic's bloody crackdown on ethnic Albanians in Kosovo, a former Serbian province that declared independence in 2006.

‘’Despite repeated attempts by the Milosevic regime to shut down his newspapers, the journalist refused to be cowed into silence and paid the ultimate price for his bravery,’’ Media Freedom Rapid Response said.

Independent journalists in Serbia still face threats from government officials and from many tabloids that are firmly under Vucic’s control.