Croatian Forces Press Serbs on Two Fronts : Balkans: Zagreb troops pound rebels near Krajina capital. Second wave is pushing into central Bosnia.

Croatian artillery and mobile infantry pressed rebel Serbs in Balkan fighting Saturday that mocked diplomats who were scrambling to head off a full-scale war between Croatia and Serb forces.

The United Nations said Croatian guns firing across the border from Bosnia-Herzegovina blasted the village of Cetina near Knin, the rebel capital in the Serb-administered Krajina region of Croatia. Other Croatian units were said to be pushing east into Serb-controlled areas of central Bosnia.

But the Serbs had the upper hand in northwestern Bosnia, where U.N. officials reported continued rebel artillery, tank and mortar fire against hard-pressed defenders in the Muslim enclave of Bihac.

Seeking to tamp the spiraling violence, Yasushi Akashi, the senior U.N. official in the former Yugoslav federation, appealed to Croatian President Franjo Tudjman on Saturday. “He urged restraint at a time of crisis,” said U.N. spokesman Chris Gunness.

U.N. military observers noted with “extreme concern” a major buildup of Croatian forces inside Croatia to the west of Krajina, simultaneous with increased pressure from Croatian advances from within Bosnia.

Observers fear that Croatia may be poised for a full-scale invasion of Krajina. That would broaden Balkan bloodshed to proportions not seen since the collapse of the Yugoslav federation.

In Paris on Saturday, French President Jacques Chirac and British Prime Minister John Major agreed to revive efforts for peace talks between the warring sides in Bosnia.

“I think we have to look again at the desirability of getting the parties to the conflict talking,” Major said after a two-hour lunch with Chirac in the Elysee Palace before going on holiday to the south of France.

“At the moment there has been a long period of silence between the parties,” he told reporters.

But European Union peace negotiator Carl Bildt said Saturday that he sees no hope of a halt to the fighting in Bosnia in the near term and that a U.N. withdrawal cannot be ruled out.

“I don’t think the different parties are ready for a cease-fire yet. They have decided to fight . . . the Bosnian government side and the Bosnian Serb side as well,” he told a news conference in Sweden.

Akashi is scheduled to travel to Knin today for talks with Milan Martic, leader of the Krajina Serbs, who occupy about 20% of Croatian territory behind 1994 U.N.-patrolled cease-fire lines, which are now in jeopardy.

Martic, who was indicted for war crimes by a U.N. tribunal last week, has protested to the Security Council that Croats are committing atrocities against Serb civilians left homeless by the Croatian advances.

“Croatia’s goal is to exterminate the Serb territories and create an ethnically pure Croatian state,” Martic said.

In a letter faxed Saturday to the U.N. commander in the former Yugoslav republics, Gen. Bernard Janvier of France, Krajina Serb army commander Gen. Mile Mrksic said that his forces would “no longer tolerate Croatian provocations and would hold the peacekeeping troops and the international community responsible for the consequences of the Croatian attacks.”

U.N. officials fear that 10,000 peacekeepers and U.N. officials in the disputed region could be taken hostage if fighting escalates.

Also Saturday, Bosnia’s Serbs, reeling from battlefield losses to Croatia’s army, appealed to the Yugoslav army to defend them in the name of ethnic ties--a move that could further spread the Balkans war.

Serb-dominated Yugoslavia, which has been presenting itself as a peacemaker in an attempt to have devastating U.N. sanctions lifted, called an emergency meeting of its top leaders. No details of the meeting were immediately available.

In May, rebel Serb forces responded to a Croatian attack by shelling the border town of Karlovac and hitting Zagreb, Croatia’s capital, with half a dozen rockets. Some dependents of American Embassy officers left Zagreb on Saturday for Vienna at U.S. government instruction.

In new trauma for eastern Bosnia, meanwhile, Bosnian Serb forces have looted and burned the Muslim town of Zepa they captured in the past week, and claim to have executed the commander of local defense forces, U.N. spokesman Alexander Ivanko said in Sarajevo on Saturday.

By Ivanko’s account, Bosnian Serb army chief Gen. Ratko Mladic told a U.N. officer that Col. Avdo Palic had been killed after an impasse was reached in surrender negotiations. U.N. officials said they could not confirm the report, but Palic had not been seen since Thursday.

“We suppose it’s true. We are quite sure he did not return from talks, so we are quite sure he is at least captured if not dead,” said Amir Hadziomerajic, a Bosnian government liaison with the U.N. mission.

Palic was considered a hard-line military commander who had resisted surrendering to the Serbs. He clashed with Zepa’s civilian leaders, most of whom were refugees and relative newcomers to the “safe area,” who were more willing to go along with a Serb-coerced expulsion.

Troops under Palic’s command were responsible for one of the Bosnian Serbs’ most stinging defeats early in the war. In June, 1992, they ambushed a convoy of Serb tanks as it entered Zepa from the north, killing more than 200 rebel soldiers and enhancing Zepa’s reputation as a tough city that could not be conquered.

The evacuation of 5,000 civilians from Zepa is complete, Ivanko said, but an estimated 3,000 civilians are still hiding out in woods and caves north of the town with an unknown number of Bosnian government troops.

As Zepa was falling, Croatian Serbs, Bosnian Serbs and rebel Muslims launched coordinated attacks on the Muslim Bihac pocket, where 160,000 people are trapped with little food.

The Croatian army assault against Croatian Serbs, which followed an agreement between Croatian and Bosnian leaders last weekend, was seen as a means of relieving pressure on Bihac, while at the same time recovering lands lost to the secessionist Serbs in six months of fighting in 1991.

The Croats captured two Serb-held towns in western Bosnia on Friday, chasing Serb civilians from their homes and severing the main supply road to Knin from Bosnian Serb territory. By Saturday, the Croatian raiders were claiming to control around 150 square miles in western Bosnia.

The “aggressors have plundered and torched all Serb settlements in the area,” a Bosnian Serb statement said.

The Reuters news service quoted Bosnian Serb army sources as saying that the Croatian forces were heading east toward the central Bosnian towns of Jajce and Donji Vakuf, which lie on a road leading north to the major Serb-held town of Banja Luka.

U.N. relief officials said 13,000 Serb civilians had fled the Croatian invaders inside Bosnia and many were sleeping in the open. The Bosnian Serb army said a total of 20,000 Serb civilians were in flight.

Bosnian government commander Gen. Rasim Delic thanked Croatian commanders Saturday for their successes, which he called “a huge step toward our joint goal of defeating the policy of the aggressor Serbs.”

The fear in diplomatic circles is that any large-scale Croatian attack on Knin would not only trigger retaliation against Croatian cities but might also drag Serbia, ultimate guarantor of rebel Serbs in Croatia and Bosnia, into armed confrontation with Croatia.

Times staff writer Tracy Wilkinson, in Vienna, contributed to this report.