MOSCOW, SEPT. 21 -- Soviet leader Mikhail Gorbachev has not appeared publicly here for six weeks, prompting rumors that he may have fallen ill.

Gorbachev, who makes frequent public appearances and often receives a stream of visitors in his Kremlin office every week, was last seen here on Aug. 7. It is the longest period he has remained out of public view since becoming the Soviet Communist Party leader in March 1985.

The West German newspaper Bild Zeitung reported today that Gorbachev fell ill of food poisoning while vacationing in the Soviet Crimea and was briefly hospitalized.

The report could not be confirmed and officials reached here dismissed it as rumor. At the same time, however, they told visiting New York Gov. Mario Cuomo that a meeting with the Kremlin leader could not be arranged, giving no explanation.

Bild Zeitung also said Soviet authorities were investigating whether the food poisoning may have been an attempt to assassinate Gorbachev, but it cited no sources for its reports.

Asked why Gorbachev's apparent departure for vacation had not been reported officially, Foreign Ministry press spokesman Boris Pyadyshev said late last week that the Soviet leader was "still on vacation."

The official Soviet news media, which customarily inform readers when the Kremlin leader leaves the Soviet capital for official trips or vacation, also have not mentioned Gorbachev's whereabouts in the past month and a half.

The state-controlled press has published a rash of letters and messages in Gorbachev's name during his absence, giving a public impression of a flurry of activity in the Kremlin. Tonight, for instance, as the rumors about Gorbachev's illness began to circulate in Moscow, a commentator began the evening television news by reading two letters from Gorbachev -- one to architects and the other to West German steel workers.

The Soviet leader also has not appeared at several public events at which he had been expected in recent weeks. Soviet officials expected him to speak at a congress of young Soviet pioneers on Aug. 30, in the Soviet city of Artec, for example, but he did not appear. The following week, editors of an American news magazine who had been told tentatively that Gorbachev would be available for a presentation they were planning in Moscow, were suddenly told that he would not be free.

Until this week, western diplomats here had speculated that Gorbachev was vacationing or preoccupied with plans for major events scheduled for later this year, including a U.S.-Soviet summit meeting in Washington. Visitors to the Soviet capital in the past month have been told that Gorbachev is unavailable because he is vacationing, a senior western diplomat said recently.

Gorbachev was last seen here on Aug. 7, in a Kremlin meeting with American schoolteachers.

Since then, various articles and letters have been published under his name, a practice that became common in the days of his predecessors but has rarely been used during his 2 1/2 years in office.

Two weeks ago, for example, the official news agency Tass released a greeting, signed by Gorbachev, to participants at an international book fair. Last week, a major article under his name was published in the party newspaper Pravda.

The last time Gorbachev was absent from public view for a long period was early in the Chernobyl nuclear crisis last year, when he did not appear publicly for 18 days.