UEFAPresident Michel Platini was quoted as saying that "violence in football is a core concern for us that needs to be addressed urgently."
Commenting on his meetings with President Boris Tadic in Belgrade and President Ivo Josipovic in Zagreb, Platini said that he had seen in his meetings with those heads of state "that they share our concerns and wishes to commit to finding solutions."
"We agreed on the need to build a strong plan of concrete measures which require strong leadership and commitment from both governments at all levels," Platini was quoted as saying.
"I must stress, however, that unless UEFA sees positive and clear signs that concrete measures are being taken within this calendar year, there is the serious risk of suspension for the national and club teams of both associations from UEFA competitions. We must see a clear improvement. If not we will not hesitate to take firm action," said the UEFA chief.
"UEFA will, in case there is no clear improvement of the situation, exclude all Croatian and Serbian teams from its competitions, meaning both national and club teams, for a long period of time."
Platini highlighted the fact "that the violence involving certain sections of supporters at matches is a matter beyond football where the intervention of the states and, in particular, the international collaboration of police forces, is a key factor for success."
An efficient plan to combat violence at stadiums should include "an effective system of banning orders, travel bans for troublemakers, the development of protocols for police cooperation and information exchange, and the swift prosecution of troublemakers, with severe penalties imposed if found guilty."
UEFA also proposes "an integrated approach to policing, security and stewarding, an improved quality of stadium infrastructure and operations, better training for police and stewards, standard use of police spotters and intelligence officers, an efficient database for troublemakers and the empowerment of friendly supporters."
During his meeting with Platini in Zagreb, President Josipovic said that he was aware of the issue of rioting at football matches and that the Croatian government had drawn up a new law expected to help solve this problem.
Josipovic said he would ask the institutions in charge to undertake all the necessary measures so as to avert hooliganism at stadiums in Croatia.