The Soviet Union said tonight that falling temperatures at the Chernobyl nuclear plant indicated the "practical termination" of the graphite fire inside the reactor.

In a statement read on the evening television news, the government also said that the release of radioactive substances from the plant had "sharply diminished."

The head of the Soviet news agency Novosti said in an interview published by the West German magazine Der Spiegel that the death toll from the accident had risen to four, Reuter reported from Bonn Saturday.

Valentin Falin, a former Soviet ambassador to West Germany, also said that the accident was caused by human error.

Tonight's statement gave no figures for the temperature inside the reactor, although figures cited earlier by Soviet officials had put heat inside at the reactor at more than 300 centigrade.

The statement also noted that "work is being done to additionally consolidate the reactor's foundation."

For the first time, radiation levels were included in the nightly statement on the Chernobyl accident. Radiation was registered at .33 milliroentgen per hour 36 miles from the Chernobyl plant and .32 milliroentgen per hour in Kiev, which, the statement concluded, is not a health hazard.

Radiation levels on the western borders of the Soviet Union were "within limits of the natural background," the broadcast said.

[Medical supplies were flown to the Soviet Union Saturday to help treat victims of the nuclear accident, the Swiss Serological Institute in Bern said. Soviet health authorities ordered about 1,125 packages of a medicine used in bone-marrow transplant surgery, Reuter reported.]