MEXICO CITY, MAY 31 -- A strong earthquake rattled Mexico's capital early today, temporarily cutting some services and sending frightened residents into the streets. No damage or injuries were reported.

There were varying reports on the strength of the 20-second quake, which struck at 1:35 a.m. local time (3:35 a.m. EDT). The epicenter was about 40 miles west of the Pacific coast resort city of Acapulco.

The quake followed several tremors on two continents in the last three days.

A tremor jolted parts of Bulgaria and Romania early today, about 14 hours after a powerful earthquake shook central Europe from the Baltics to the Black Sea, killing at least 11.

In Romania, nine people died and 994 were injured, the health ministry said. Most were hit by falling rubble. One person died in Soviet Moldavia and one, of a heart attack, in Bulgaria.

In northern Peru, dozens of strong aftershocks struck Amazon villages after a major quake tore through the region Tuesday night, killing at least 101 people, civil defense officials said.

A series of small earthquakes also shook Costa Rica Tuesday and Wednesday but caused neither injuries nor damage.

In Mexico, local television reported that the U.S. National Earthquake Information Center had measured the quake at 6.1 on the open-ended Richter scale. Television later quoted the University of Mexico's seismological service as measuring the tremor within the capital at 5.5 on the Richter scale, while the official Tacubaya Seismological Center registered it at 4.9.

Police, Red Cross and hospital spokesmen in the capital and in Acapulco said there were no reports of injuries or damage to buildings.

But the jolt frightened many, especially in the old colonial center of Mexico City, parts of which were devastated by an earthquake in September 1985 that left thousands dead.

There was no visible damage to that area, where some of the rubble of the 1985 quake still has not been cleared away.

In at least two major hotels, nervous guests gathered in the hallways after the tremor struck. Parts of the capital reported temporary power and water outages.