The Soviet embassy accused Greenbelt police yesterday of harassing a senior Soviet diplomat who was accused of shoplifting Friday in a Greenbelt department store.

A statement from the embassy called the charges against the diplomat "false and null," and characterized the incident as "an outright provocation."

A State Department spokesman, while declining to comment on the specific incident, said, "shoplifting is a clearly unacceptable form of behavior for a diplomat."

The embassy staff member, who police, State Department and Soviet Embassy spokesmen declined to identify, was stopped briefly Friday at Marshall's in the Beltway Plaza Shopping Center, according to police. Police said the man had concealed two belts, a woman's swimsuit and a vase under his clothing. He was released after the goods were recovered. No charges were filed because of the man's diplomatic immunity, police said.

Yesterday's statement by the Soviet embassy acknowledged that a senior diplomat had been detained, but said that "from the very beginning, there was absolutely no ground for his detaining and all the charges against him are false and null. We qualify this whole incident as an outright provocation as it was stressed in the Embassy note to the State Department.

"In this note we also demanded to take appropriate steps against those responsible for the harassing of a Soviet diplomat," the statement said.