LJUBLJANA, Yugoslavia (AP) _ The government of the northern republic of Slovenia said Friday that Serbia, in the south and east, is attempting to ''oust us from Yugoslavia.''

The statement from the Slovenian presidency followed Serbia's decision Tuesday to ban all political and economic contacts with Slovenia.

Liberal, prosperous Slovenia and the hard-line communist leadership of Serbia have been feuding for years. But the Serbian action Tuesday was the gravest threat to the unity of the Yugoslav federation since the death of the nation's post-World War II leader Josip Broz Tito in 1980.

Earlier Friday 13 people were arrested when police dispersed a crowd of about 100 gathered for a pro-Serbian rally in Ljubljana that had been prohibited by Slovenian authorities. Slovenia issued an order Tuesday banning the rally and Serbia reacted by severing relations with Slovenia.

In its statement, Slovenia's collective presidency called Serbia's action ''a flagrant violation of all constitutional, legal and civilized norms.''

''We shall never permit anyone to drive us away or oust us from Yugoslavia,'' it said.

''Yugoslavia is our country. We have the right to be citizens of the Socialist Republic of Slovenia and also to be different. Those who do not acknowledge this separate themselves from the federal state.''

It denounced the Serbian communist leadership, saying, ''We do not accept a comprehensive control of a single truth, of political uniformity, authoritarianism and intolerance, of ideologic monolithism.''

Serbia is the largest of Yugoslavia's six republics.

Aleksandar Prlja, Serbia's secretary for foreign affairs, told The Associated Press that Slovenia's ''banning of the peaceful rally was deeply humiliating for the Serbian people.

''This is irreconcilable with joint existence in a federal state.''

Slovenian officials said the rally had been organized by Serbian politicians trying to oust the Slovenian leadership.

Economic decline has brought increased friction between the republics with their different ethnic populations, and the Slovenian Serbian conflict also involves liberal vs. conservative communist leaders. Slovenia advocates regional autonomy and has legalized opposition groups that will contest the region's first multi-party balloting in elections next spring. Serbia insists on a centralized federtion with the Communist Party the only official party.

The Serbian news media on Friday accused Slovenia of ''fascist-like'' behavior and called for the resignation of Yugoslav President Janez Drnovsek, a Slovene.

Delo, Ljubljana's major newspeper, said Friday's rally was ''an integral part of a plan to alter by force the Yugoslav federation. It was yet another attempt to bring Slovenia to its knees.''

It called Serbia's imposition of an economic boycott a ''declaration of war'' and said Slovenia would respond by ''opening itself to the world, introducing greater democracy and by holding free elections.''