A severe earthquake hit several cities in the Soviet Central Asian republic of Tajikistan last night, leaving an undisclosed number of dead and injured, the official news agency Tass reported today. It was the most powerful quake to strike the Soviet Union in nearly a decade, according to records here.

Seven successive tremors hit Leninabad and two other cities in the earthquake-prone region at 10 p.m. local time (12 noon EDT), a dispatch from the Tajikistani capital of Dushanbe in today's edition of the government newspaper Izvestia said. The quake caused landslides, destroyed roads and reduced clay houses to rubble, a Soviet official told Reuter news agency.

A Soviet seismological official said the quake measured 6.1 on the open-ended Richter scale, which would make it the worst in the Soviet Union since 1976, when an earthquake killed an undisclosed number of people in the city of Gazli in Uzbekistan, also in Central Asia.

In Golden, Colo., the U.S. Geological Survey's National Earthquake Information Center measured the tremor at 5.8 on the Richter scale. A center spokesman described the quake as "moderate," United Press International reported.

The first of two earthquakes in Mexico City last month, in which more than 7,000 persons are believed to have died, measured 8.1 on the Richter scale.

In its unusually descriptive report, Tass said the disaster wiped out industrial buildings, homes and cultural facilities. Around the town of Kayrakkum, where damage was heaviest, "adobe houses were destroyed in villages, and a landslide swept away an asphalt-surfaced road," Tass said. The main quake demolished a hospital just south of Kayrakkum, which had been evacuated by patients and staff, Izvestia said. The quake also ripped out telephone lines to Leninabad, a city of 125,000, a Moscow telephone official said.

Izvestia said local authorities had been aware of the possibility of a quake because of a sharp temperature drop and and other climatological changes.

The urgent tone of the Soviet dispatches on the disaster, referring to "loss of life," toppled buildings, and "emergency" rescue operations, suggests that casualties were high and damage was extensive, as did the announcement that the Soviet leadership had sent its condolences to the families of the victims. In keeping with Soviet practice, no casualty toll was released. Tass also said that "the necessary aid is being given to the quake victims."

Soviet television showed pictures tonight of rescue efforts in Leninabad, where carpet and silk manufacturing complexes were damaged severely. Rescue workers were shown digging in the rubble of a carpet factory, and cracks more than two feet wide were seen to have appeared in the ground.

The eight-point Soviet rating of the earthquake on a 12-point scale is one indication of its severity. The measurement refers to a destructive force powerful enough to knock down monuments.

In the Gazli disaster nine years ago, 10,000 persons were left homeless.

Tajikistan, the small republic where the quake occurred, is a dry, often brittle area bordering on China, Afghanistan, Pakistan and India. Tremors were reported in Tajikistan as recently as last month.

The quake epicenter was at Kayrakkum, a town 25 miles east of Leninabad with a population of 32,000, according to Izvestia. Smaller jolts of 3 to 5 points on the Soviet scale also hit Dushanbe and the Uzbekistan capital of Tashkent, according to Tass.

The relative frequency of earthquakes in the Central Asian republics of the Soviet Union has led to efforts to design buildings able to withstand strong tremors.