Romanians struggled today to recover from the earthquake that devastated this Eastern European capital. Hospital officials said 4,000 or more persons died in the disaster, which may have left more than 80,000 homeless.

Romania appealed to the United States and the United Nations to send medical supplies and other relief.

The government said 12,000 apartments or houses had been evacuated. But Western diplomats said 20,000 apartments in Bucharest alone were uninhabitable.

After President Nicolae Ceausescu inspected ruins in Bucharest and found a new computer center and 16 wrecked apartment houses had been poorly built, he demanded an investigation "for the guilty to be most severely held responsible," the official Agerpress news agency said. The official Communist Party newspaper Seinteia said the national nuclear center had also been destroyed, and important chemistry research facilities at Bucharest University.

The government officially confirmed 746 dead, most of them in the capital. Another 5,642 persons were injured, nearly half of them seriously.

But hospital officials and foreign medical students working in the city's 40 hospitals estimated the toll of dead would go over 4,000. They said 1,000 dead were in one hospital alone.

Foreign Minister Manea Macoverscu summomed U.S. Ambassador Harry G. Barnes Jr. and formally requested American medical supplies, some of which probably will be sent from Italy. Barnes offered $25,000 worth of aid yesterday. France and West Germany also were expected to help. The New China News Agency praised "heroic Romania" in a dispatch from the scene.

Temporary housing was being erected in schools, dormitories and new apartment blocks stil under construciton. Tens of thousands of Burcharest's 1.7 million residents mailled aimlessly in the streets, afraid to return to their homes until they are inspected and declared safe.

The state radio ruged people to boil water for 10 minutes before use. Bottled mineral water and 400 tons of bread were trucked to the capital.

The bleak picture was brightened by the discovery of survivors. A 7-year-old boy and his grandfather were pulled from the smoking ruins of their six-story apartment building. It seemed inconceivable that anyone could have survived for 36 hours under the pile of plaster, bricks and stones. Three other persons were found alive in the same pile of rubble.

Agerpress reported major damage in the northeastern town of Jasi, close to the Soviet border, and the steel center at Galati.

Buzau, 62 miles north of Bucharest, suffered extensive damage, but peasants' homes in the countryside appeared unscathed except for an occasional toppled brick chimney. Power lines were up and trains were running.

Michael Dobbs of the Manchester Guardian reported from Bucharest:

So far the Romanian authorities have underplayed the extent of the fatalities, presumably in the belief that premature speculation about the number of people still unaccounted for might cause unnecessary alarm.

Large crowds gathered outside hospitals hoping to hear news of relatives or to identify bodies. In one hospital I visited, the 50 members of the medical staff had been working virtually without a break since the earthquake struck Friday night.

Many patients were suffering from horrible injuries, particularly to the head and legs, caused by falling to the ground from a considerable height. Most of the survivors were from upper stories as those wiht apartments nearer the ground were buried deep in the rubble.

Reports of extensive damage have been coming in from other parts of Romania - particularly the industrial city of Craiova, 200 miles west of Bucharest.

The government has also reported fires and explosions in a petrochemical complex and oil refinery in Ploesti, 40 miles north of here. A sulphuric acid plant was heavily damaged.