A major earthquake struck southeastern Europe yesterday.Romania reporting "human losses and considerable material damage," declared a state of emergency.

The sharp, lengthy and widespread tremors shook buildings from Moscow to Rome. Injuries were reported in Yugoslavia and power failures occured in Bulgaria.

Bucharest Radio, monitored in Belgrade, broadcast a decree mobilizing the armed forces, government agencies and Communist Party activists.

Seismologists reported that the quake which struck at 12:12 p.m. EST measured between 7 and 7.5 on the open-ended Richter scale - an intensity that could cause serious damage and casualties, they said.The earthquake in China last year that killed more than 600,000 measured 8.2.

"We don't have any official figures but in the talk around here, the estimate is in the hundreds of dead, if not more," said a Marine guard reached by phone at the U.S. embassy in Bucharest.

The Guard said the capital's central old section was almost destroyed. "You can hear sirens running around. The people are all in the streets and the rescue teams are trying to do what they can in the darkness with all the lights out."

Another embassy official said all of U.S. contingent in the Romanian capital, about60 families in the city of 1.5 million people, were safe. He said an embassy annex suffered "heavy damage."

An operator of the Bucharest telephone exchange said, "There was a noise - a terrible noise. Then I was 'dancing.' The shock made us dance." She said there were many deaths and injuries.

The U.S. Geological Survey put the epicenter of the quake beneath the Carpathian Alps in northeastern Romania, about 120 miles north of Bucharest, an area known as Transylvania.

The Physics Institute of Strasbourg, France, said the tremors were the most violent in Eastern Europe since Nov. 10, 1940, when a quake caused severe damage throughout the area.

Shortly after the quake all telex and telephone connections with Romania were interrupted and all outside calls - including official ones - were canceled for the night, the Vienna telephone exchange said.

Bucharest Radio went off the air in the middle of a newcast when the quake struck. It resumed broadcasting nearly two hours later with exhortations to the public.

The radio said Romania's Communist leaders called on the entire population "to act in calm and order and to support the rescue teams in order to radicate as speedily as possible the aftermath of the earthquake."

It warned against "parking or waiting near seriously damaged houses or buildings" and urged people to "participate in the clearing of debris."

Several people were reported injured in Yugoslavia, at least one of them seriously, the official Yugoslab new agency Tanjug reported from Belgrade.

It said 17 persons requested medical assistance in Kragujevac, a city south of Belgrade near the Romanian border. Yugoslav officials said tremors cracked walls in old buildings and sent people fleeing into the streets in Belgrade, Sarajevo and Zagreb.

Tanjug reported from Sofia, the Bulgarian capital, that the quake sent residents there out of buildings and occasionally interrupted electrical and telephone transmissions.

The Hungarian news agency MTI said "residents of multi-story houses ran into streets" there and factory work came to a standstill in cities near the Romanian border.