The embattled Croatian republic has endorsed a European Community proposal for an international peace conference on Yugoslavia and the deployment of Western cease-fire monitors, officials said Friday.

The EC plan has not been accepted, however, by Yugoslavia's largest and most powerful state, Serbia, whose hard-line leadership has in the past rejected foreign involvement in Yugoslavia's internal affairs.Croatian leaders also praised the EC's refusal to accept the alteration of Yugoslavia's republic borders by force, the state news agency Tanjug said.

EC observers have already been deployed to monitor the truce in the northern state of Slovenia, where fighting briefly raged after it too declared independence from Yugoslavia.

The fighting in Croatia has been far more serious and prolonged. It pits Croatian militias against Serbian guerrillas backed by the Yugoslav army. Croatia sought independence after Yugoslavia rejected a proposal to transform the nation into a loose federation. Minority Serbs in Croatia want their territory to remain part of Yugoslavia or even Serbia.

Meanwhile, gunfire and explosions were heard Friday outside Vukovar, 25 miles southeast of Osijek on the Danube border with Serbia. Croatian guardsmen told reporters that federal army tanks were advancing toward the town.

In Belgrade, about 1,000 mothers of conscripts serving in the Yugoslav army continued to protest Friday in a military barracks.