About 13,000 workers went on strike in Belgrade's main industrial suburb Monday in the most serious walkout to date prompted by the failure of the Serbian Republic's Marxist regime to pay back wages to hundreds of thousands of state enterprise employees.

Workers at engine, tractor, refrigerator and machine tool factories in Rakovica, 6 miles southwest of downtown Belgrade, reported to their plants but refused to perform their jobs, demanding their January wages, said Dobrivoje Lazarevic, an official of the strike committee of the Rakovica Trade Union.He said the estimated 13,000 strikers also called on managers to

replenish raw material stocks, shortages of which have caused precipitous production declines that forced several small factories to place employees on forced leaves of absense last month.

"We want conditions for what should be a normal production program, and we want our salaries paid without any reduction," said Lazarevic.

The average worker in Rakovica is owed a January salary of $350 before the Yugoslav currency was devalued on Jan. 1 by 22.2 percent.

Lazarevic said the new Serbian government of Marxist President Slobodan Milosevic, which was sworn in Feb. 11 following unprecedented multiparty elections in December, should boost the average wage to about $700 per month until it develops a way of coping with the republic's economic problems.

He also said the prices of basic foods should be reduced and frozen at pre-devaluation levels, and taxes should be slashed.

The demands reflect the gravity of Yugoslavia's economic situation, which many experts fear will fuel already-high ethnic tensions threatening the nation of 23 million with civil war.

The national economy has deteriorated because of the republics' failures to anticipate and refusals to follow Western-style reforms that were implemented in 1990 by federal Prime Minister Ante Markovic and designed to ween the nation away from 45 years of communism.

The reforms included a tightening of monetary policy that restricted the printing of new money and the awarding of loans to enterprises regardless of their financial health - the traditional tools by which cash shortages were made up and politicians maintained power. But they also fueled hyperinflation.