20 Killed as Fighting Spreads in Croatia : Yugoslavia: The breakaway republic’s nationalist president sends new ultimatum to federal leaders in Belgrade.

BELGRADE, Yugoslavia —  Fighting spread across the breakaway Yugoslav republic of Croatia Thursday, and about 20 people were reported killed.

Scores of people were reported wounded in the increasing bloodshed and Croatia’s nationalist President Franjo Tudjman sent a new Aug. 31 ultimatum to federal leaders in Belgrade to settle the conflict or face a bigger catastrophe.

The clashes underlined the helplessness of the federal presidency to halt the bloodshed, despite agreeing with the heads of the six republics on moves toward a new peace plan at their latest summit Wednesday.

Serbian television said eight Serbian civilians were killed and 10 wounded when Croatian national guard forces stormed the village of Kinjacka, southeast of the Croatian capital of Zagreb.

It also said six bodies washed up on the Danube River bank near Bogojevo, on the Serbia-Croatia border.

Police and hospital sources said three Croatian guardsmen were killed and 17 wounded in battles Thursday around Sisak, southeast of Zagreb.

Other deaths and scores of wounded were reported by local sources and radio in all three regions of Croatia where Serbian guerrillas are fighting to keep Serb-populated areas inside Yugoslavia in conflict with Zagreb’s June 25 independence bid.

Croatia’s top leadership organ, the State Council, declared Wednesday’s meeting of the federal presidency a failure and said it had stepped up defenses in the republic.

Croatian television reported Tudjman as saying he had sent a letter to the collective Yugoslav presidency, which meets in Belgrade Friday.

In it he demanded that the presidency make the Serbs lay down their arms and accept a cease-fire, and force Serbia to stop backing the Serb uprising and seizing territory in Croatia.

He also demanded that the federal army be returned to barracks and that the armed forces be reduced to peacetime levels.

Tudjman said that if his demands are not met, the army would be viewed as an occupying force in Croatia and “serious measures will be taken.”

A witness to heavy fighting Wednesday in the east Croatian town of Pakrac said the town’s police station had been destroyed and police ducked and dived to avoid repeated attacks from Serbian snipers.

Bullet holes, trails of blood and broken windows scarred the main street, and some shops had been looted. The witness said two corpses lay in the town center, one with its head split in half by an ax.

Most civilians had already abandoned Pakrac, where fighting continued Thursday. Some 100,000 people have fled the fighting across Croatia over the last few months.

Croatian television also showed federal warplanes rocketing the semi-deserted village of Sarvas, near the strategic town of Osijek, for a second day.

Croatian radio said some residents of Sarvas, evacuated earlier this month, had returned to feed farm animals at the time of the raid.

The chief of the general staff, Gen. Blagoje Adzic, denied in a Belgrade newspaper interview that the army was taking the Serbian side. He said it was only trying to keep the warring groups apart.