MOSCOW, May 24 (RIA Novosti) - Russia's chief sanitary official on Sunday advised Russian citizens against visiting Japan, where human cases of the swine flu virus have been registered.

Gennady Onishchenko told RIA Novosti that Russians should not visit the country for non-essential trips. Onishchenko earlier issued similar warnings on travel to the United States, Mexico, Canada and Spain.

According to the World Health Organization's latest update, a total of 12,022 people in 43 countries worldwide have been officially diagnosed with the A/H1N1 swine flue virus, with 86 deaths.

Russia's Health Ministry said on Friday that the first case of human swine flu infection had been diagnosed in Moscow.

"According to a statement by the chief doctor of the First Infectious Diseases Hospital, a patient has been hospitalized... and was put directly into an isolation ward," the spokesman said.

The man, who recently visited the U.S. is in a stable condition with a normal temperature, he said.

The U.S. government has allocated $1 billion to companies involved in A/H1N1 vaccine research.