THE HAGUE (Reuters) - The Yugoslavia war crimes tribunal said on Friday it had urged three former Yugoslav army officers charged with responsibility for a massacre near Vukovar in Croatia in 1991 to surrender themselves for trial. The U.N. court said it had ordered Yugoslavia to serve notice on the three men to turn themselves in to stand trial along with a fourth suspect in the case later this month. The three men are Mile Mrksic, Miroslav Radic and Veselin Sljivancanin, who held the respective ranks of colonel, captain and major in the Yugoslav National Army (JNA). The tribunal issued indictments against them in November, 1995. The Yugoslav National Army and Serb forces besieged Vukovar after Croatia declared its independence from Yugoslavia in June, 1991. They captured the city in November of that year. Tribunal prosecutors allege that JNA and Serb paramilitary soldiers under the command of the three officers took around 200 Croats and other non-Serbs from a hospital in Vukovar and systematically killed them at a farm in nearby Ovcara. Two hundred bodies were dug up from a mass grave at Ovcara in September and October, 1996. Slavko Dokmanovic, a Serb arrested last June in the East Slavonia region of Croatia, is accused of aiding and abetting the killings while mayor of Vukovar. Dokmanovic is due to go on trial on January 19 and has already pleaded not guilty to the charges against him. The tribunal has condemned Belgrade in the past for failing to hand over the other three suspects in the case who are believed to be living in Yugoslavia.