A Soviet tug arrived this morning and took in tow a Soviet nuclear submarine that was cast adrift yesterday off Okinawa after a fire reported to have taken the lives of nine crewmen.

Japanese officials said initial tests by planes and ships monitoring the accident indicated no abnormal level of radiation. The Foreign Ministry asked the Soviet Embasy here for a full account.

The Japanese Defense Agency warned ships to avoid the area because radiation spillage could not be ruled out. Cabinet Secretary Kiichi Miyazawa said that if there was a leak, the route by which the sub was towed could "pose a problem."

Officials said 55 survivors were evacuated yesterday by the Soviet cargo ship Meridan, leaving a skelton crew aboard the 375-foot submarine, Its crew had refused Japanese offers of assistance.

The sub apparently is to be towed back to its eastern Soviet port of Viadivostok, about 1,200 nautical miles away. The obsolescent Echo-class craft normally carries a crew of about 100.

The captain of a British tanker that was first on the scene was quoted as saying the Soviet officers told him there had been a fire, but did not say what caused it or how much damage resulted.

The tanker Gari sped to the spot in international waters 84 miles east of the Japanese island of Okinawa after sighting distress flares shortly after dawn yesterday.

Officials of the Japanese Maritime Agency said intercepted Soviet radio traffic reported at least nine crew members dead and three injured aboard the $6,000-ton undersea vessel.

When the Gari arrived, "the submarine apparently was without power of any kind but at the same time there was no sign of a fire on board," said a Tokyo spokesman for the tanker's owners.

The spokesman said three Soviet officers went aboard the Gari and requested drinking water and permission to use the radio to send a message to the Meridian, but they asked for no other assistance.

Dead and injured could be seen on the deck of the submarine, he said.

While awaiting arrival of the 4000-ton Meridian, which was a few hours away, the Soviets also refused help from a Japanse patrol craft that sped to the scene from Okinawa. The Japanese said they were not allowed to board the crippled sub.

The Meridian reached the scene in early afternoon, and took aboard several dozen submarine crew members, many of whom by that time had gathered on deck under a makeshift canopy to shelter them from the sun.

Many wore white cloaks that appeared to cover their bodies and heads and seemed to be segregated from the other. This raised questions about the nature of the accident.

Japan's Kyodo news service quoted unnamed authorities of the National Science and Technology Agency as saying the protective clothing might indicate that the sub's interior had been "polluted" by radioactivity or poisonous gases from the bruning of cables.

The Maritime Safety Agency, Japans coast guard, sent three othe ships to the scene to test for radiation and collect water samples, while an aircraft monitored the air overhead. The crew reportedly shot flares to interfere with efforts from light planes to photograph the sub.

The agency identified the sub as one of the Soviets' aging Echo 1 class, built in the 1960s and superseded within a few years by more advanced models. The craft normally carries a crew of about 100. Officials said only about five such subs are now in service.