Serbian Forces Step Up Attacks on Bosnia : Balkans: Sniper fire and shelling terrorize the capital. President of the new nation pleads for international aid.

Serbian radicals and Yugoslav federal troops stepped up attacks on newly independent Bosnia-Herzegovina on Wednesday, terrorizing Sarajevo, the capital, with sniper fire and indiscriminate shelling.

At least 30 people have been killed in Sarajevo over the past few days, and some reports put the republic-wide death count from a week of violence as high as 300.

News agencies reported from Sarajevo that streets were virtually abandoned because of relentless shooting and mortar fire from Serbian-controlled villages in the mountains around the multiethnic city.

A third night of curfew and blackout was ordered to deter further clashes, and all but essential businesses have closed.

Militant Serbs and army troops supporting them had warned of civil war if Western countries recognized Bosnia-Herzegovina as an independent country after a referendum five weeks ago in which two-thirds of the republic endorsed secession.

The 12-nation European Community announced Monday that it is establishing diplomatic relations, and the United States followed suit Tuesday, signaling that the West would not be cowed by the Serbian minority’s threats of aggression.

The recent assaults, combined with political maneuvers in Belgrade, appeared to be the start of an all-out Serbian offensive to take over most of Bosnia-Herzegovina so that the land can be joined with Serbia, Montenegro and areas of Croatia conquered and occupied during last year’s war.

Bosnia’s Muslim president, Alija Izetbegovic, appealed for international help in quelling the deadly insurgence.

“Radical elements cannot reconcile themselves with the international recognition of Bosnia-Herzegovina and are constantly escalating the violence,” Izetbegovic said in an appeal to the United Nations, the European Community and the United States “to intervene and prevent the forces of violence from overcoming democracy.”

Serbian President Slobodan Milosevic and the hard-line Communist high command of the federal army have assured the United Nations that they will comply with a costly mission deploying 14,000 “blue helmet” peacekeepers to halt fighting in Croatia.

But the Belgrade authorities, acting in the name of crippled federal institutions, have been openly supportive of the Serbian insurgents wreaking havoc in Bosnia-Herzegovina.

The federal Parliament, which is boycotted by all ethnic groups except Serbs and the closely related Montenegrins, decreed Wednesday that “federal laws” apply in Serbian-held areas of Bosnia-Herzegovina.

It remains unclear how much of the republic’s territory is in the hands of the Serbian guerrillas. But Belgrade-supported paramilitary units control large areas surrounding the northwestern city of Banja Luka plus the northern region bordering Serbia, and they have de facto reign over other important cities, such as Mostar, by virtue of huge deployments of federal troops fighting on their side.

Federal forces retreating from Croatia as the U.N. troops move in have largely relocated to Bosnia-Herzegovina to join 150,000 federal soldiers already in the republic.

After intense fighting that Sarajevo television reported had taken 200 lives, the army announced that it had captured the town of Kupres, a Croatian-inhabited region that hosts some of the army’s most important munitions factories.

“After two days of fierce clashes, Kupres has been under the control of Yugoslav army forces since 5 p.m. on Tuesday,” the Belgrade-based Tanjug news agency reported.

Although the army has a sizable presence in Bosnia-Herzegovina, it is believed to be sharply split between pro-Serbian units and those committed to protecting all ethnic groups in the republic.

As a republic of Yugoslavia, Bosnia-Herzegovina was a microcosm of the multiethnic federation, with no single nationality comprising a majority of its 4.4 million people. Neither did any one ethnic group numerically dominate Yugoslavia, which was home to 24 million before a fever of nationalism fueled secessionist drives.

Many of Yugoslavia’s 10 million Serbs oppose the breakup of the federation because they live scattered among several republics and do not want to become a minority population in the newly independent states. Rather, they seek to build a new Yugoslavia in which they will dominate in the wake of Slovenian and Croatian secession and the forced migration of non-Serbs from the Croatian and Bosnian territories they have seized.

Bosnia’s Slavic Muslims and Croats, who respectively account for 44% and 17% of the republic population, voted for independence to escape incorporation into the new Serbian-dominated federation Belgrade seeks to create.