Belgrade , Serbia ( CNN ) -- Clashes between Serbian police and protesters broke out Sunday in Belgrade after an ultranationalist party demonstrated against the arrest of genocide suspect Ratko Mladic . Nearly 20 people were injured in the violence -- seven police and 12 civilians -- according to police . They said they made more than 100 arrests . Mladic , wanted by the International Criminal Tribunal for the former Yugoslavia in connection with the 1995 Srebrenica massacre , was captured Thursday after nearly 16 years in hiding . The Serbian Radical Party held its protest Sunday in front of Serbia 's parliament building . Despite calls for calm from the event 's organizers , demonstrators on the fringes of the rally threw rocks at police . Hundreds of officers , some in riot gear and others on horseback , moved in against the crowd . Some beat and kicked protesters . Police stayed on the streets as the demonstrators scattered . `` We are gathered here to peacefully protest the betrayal by ( Serbian President ) Boris Tadic and his bosses in Brussels , '' party leaders told the crowd before the clashes erupted . `` We have had enough economic humiliation by our enemies , who are destroying our country ... in every way . '' At the protest -- which was attended by members of Mladic 's family and thousands of others -- speakers demanded that Tadic step down and asked that elections be held immediately . Mladic 's son , Darko , told the crowd that his father is sick . `` He needs medical treatment that he is not getting , '' the younger Mladic said . He described his father as `` a freedom fighter , '' and said he had `` defended his own nation , defended his people , which was his job . '' The younger Mladic called on protesters to keep their demonstration peaceful . `` Tomorrow if I 'm able to visit my father , I will tell him of this and he will cry again , '' he said . Mladic gave himself up without a fight , despite having two handguns , according to Rasim Ljajic , the government minister in charge of searching for fugitive suspected war criminals . Officials located Mladic in a village called Lazarevo , north of the Serbian capital , after culling information from his former comrades , those who supported him financially and his close family members , Ljajic said . It is not clear what source led investigators to the former military commander , accused of ordering the 1995 massacre of some 8,000 Muslims in the eastern Bosnian town of Srebrenica . His arrest clears a major hurdle that once stood between Serbia and its long-awaited entrance into the European Union , but the move could also usher in political backlash from the country 's electorate , some of whom consider Mladic a hero . `` We 're conscious of this danger , '' Ljajic told CNN Saturday . `` We know we did something that did n't bring us joy or applause from the public . But we also know that we took great responsibility and did something that the political elite of any country is supposed to do . '' He called Mladic 's capture `` a political investment , '' noting the government 's desire to bring the war crimes suspect to justice `` even if citizens punish us in the next elections . '' The massacre at Srebrenica , which sparked international outcry and preceded a NATO bombing campaign , is now remembered as the worst atrocity in Europe since World War II . Mladic allegedly presided over the five-day slaughter in July where Muslim men and boys were systematically executed in what was described at the U.N. war crimes tribunal as `` the triumph of evil . '' Mladic 's forces encircled the town , a U.N.-declared `` safe area '' where thousands of Bosnian Muslims had sought refuge , allegedly conducting wholesale slaughter and rape , despite the presence of a few hundred lightly armed Dutch U.N. peacekeepers charged with protecting the area 's residents and its refugees . The former general is considered the last of the fugitive war criminal suspects in the region , following the capture of Bosnian Serb leader Radovan Karadzic and former Serbian President Slobodan Milosevic , who died in jail in 2006 during his trial at The Hague . At the rally Sunday , a defiant Darko Mladic told the crowd , `` We will never accept those who bombed us to write our history . For centuries we have been fighting for our own state , for our own country to give us security . We do n't allow illiterate Westerners to write our history . '' A medical team has determined that Mladic is healthy enough to be extradited to face a war crimes tribunal , a court spokeswoman in Belgrade said Friday . While the war crimes suspect suffers from several chronic conditions , the team said there are no immediate problems barring a move . This comes after five doctors examined Mladic Thursday night , according to the ex-general 's lawyer , Milos Saljic . CNN 's Ivan Watson contributed to this report .
NEW : Nearly 100 people are injured as protesters , police clash in Belgrade . NEW : Police make more than 100 arrests . Demonstration calls for President Boris Tadic to step down . President Mladic was captured , after 16 years in prison .