Thousands of mourners gathered in Belgrade, the capital of Serbia, on Monday for the funeral of Ratko Mladic, bowing their heads in respect before the coffin of the former Bosnian Serb general and convicted war criminal known as the “Butcher of Bosnia.” Serbia’s strongman president, Aleksandar Vucic, a onetime champion of Mr. Mladic, who died Aug. 27 in custody in The Hague, stayed away from what the government insisted was a private, rather than state, event. But state-controlled television and media outlets close to Mr. Vucic hailed the former general as a hero, without mentioning his conviction by a Hague Tribunal for genocide, crimes against humanity and other offenses. After the service, soldiers in camouflage uniforms and helmets carried the coffin out of St. Luke the Apostle church to a nearby cemetery.

Among those paying their respects at the Orthodox church were Mr. Vucic’s son, Darko; several ministers, including the head of defense; and Aleksandar Vulin, a longtime ally of the president and former senior official who has pushed for close ties with Russia. The Hague court, Mr. Vulin said, “was created not to seek justice, but to seek revenge against the Serbs.” The head of the Serbian Orthodox Church, Patriarch Porfirije, led the funeral service. The death of Mr. Mladic in The Hague, where he was serving a life sentence, exacerbated an already tense political atmosphere in Serbia, where student-led protesters have been staging on-and-off street rallies, often huge, against Mr. Vucic for 20 months and where bitterly divided political parties are gearing up for parliamentary elections next month.

Monday’s funeral added further strain to Serbia’s relations with the European Union, which it has applied to join but whose terms of entry it has often defied. The European mission in Belgrade issued a statement Monday warning that “any glorification of war criminals, denial of genocide and revisionism are contrary to the most basic European values and have no place in the E.U. or in E.U. candidate countries.” Mr. Mladic’s family said he would be buried next his daughter, Ana, a medical student who killed herself in 1994 with his military pistol, apparently distraught by her father’s actions during the Balkan Wars of the early 1990s following the collapse of Yugoslavia. Mr. Vucic has sought to balance the demands of his nationalist political base, which reveres Mr. Mladic as a righteous defender of ethnic Serbs, with his desire for money from the European Union, which on Friday said the return of Mr. Mladic’s body to Belgrade “reminds Europe of the darkest pages in our recent history” and condemned “the glorification surrounding his death.” In 2017, The Hague Tribunal convicted Mr. Mladic on war crimes and genocide charges relating to the 1995 Srebrenica massacre, in which some 8,000 Bosnian men and boys were killed, and the siege of Sarajevo, the capital of Bosnia, in which 10,000 people died, including 1,500 children. For Serb nationalists, however, he is hero who has been smeared by Serbia’s enemies.