In some of the most intense fighting in months, Serb forces backed by tanks advanced Sunday on ethnic Albanian rebels, who resisted government efforts to clear key roads in rebellious Kosovo province.

Explosions and the rattle of automatic gunfire reverberated through the hills west of Pristina, the provincial capital, and smoke rose from red-roofed villages. Both sides acknowledged casualties in the fighting, which has raged since Friday night along at least three fronts.No reliable, independent casualty figures were available. Nervous Serb police turned back reporters who tried to reach the fighting.

The offensive - the most widespread and coordinated Serb operation since April - appeared aimed at clearing Kosovo Liberation Army fighters from three strategic highways: one westward from Pristina to Pec, another south to the town of Prizren and a third along the Albanian border in western Kosovo. The KLA is fighting for independence for Kosovo.

If successful, the operation would split the estimated one-third of the province under rebel control and block routes to their sanctuaries in neighboring Albania, from which the insurgents smuggle wea-pons.

Rugova's top aide, Fehmi Agani, told The Associated Press that the offensive appears aimed at gaining a clear advantage on the battlefield before peace talks, which the Americans and Europeans are trying to broker.

"Milosevic is trying in every way and at all costs to secure a superior position before possible negotiations," Agani said. "It has always been his position to negotiate from a superior position."

Early Sunday, the fighting spilled across the Albanian border, with Yugoslav and Albanian officials reporting an exchange of fire.

There was no report of casualties and each side blamed the other for shooting first. The incident heightened fears that fighting could spread elsewhere in the volatile Balkan region.

The Serbian government's Tanjug news agency said police drove KLA fighters from the villages of Banja and Zociste, site of a Serbian Orthodox monastery that the guerrillas had controlled since early this month.

The Serbian Media Center said two policemen have been killed and another two were wounded in fighting south of Pristina toward Prizren. Serb sources claimed 11 Albanians died in fighting south of Pristina, while another 20 surrendered to government forces in western Kosovo.

In its account, the Kosovo Information Center, run by independence-seeking Albanians, reported "at least" 10 Serb policemen have died in the fighting. The Albanians put KLA losses at one dead and one wounded.

The Albanian center also said eight Albanian civilians have been killed and about 40 wounded in two days of fighting across the province, where Albanians make up 90 percent of the population.