The Russian government's Epidemiology Service on Sunday officially recommended its citizens avoid visiting Spain which has 100 confirmed influenza A/H1N1 cases, according to Spanish media.

"A hundred flu cases is something serious," said Guennadi Onischenko, head of the epidemiological service. "We are asking our citizens to cancel trips to Spain."

Russian airports already have strict controls on passengers who began their journey in the Americas and are landing or changing planes in Russia.

Onischenko said that the service had examined around 6,000 passengers in the last 24 hours and no single case of the new deadly strain had been spotted.

According to official statistics, there are some 500,000 Russian travel to Spain every year.

Russia has also issued travel warnings on the United States, Mexico and Canada.

The World Health Organization has earlier confirmed 8,451 cases in 36 nations, with the United States as the most infected nation with 4,714 cases, followed by Mexico with 2,895 and Canada with 496.

Mexico's flu death toll is the highest, 68, followed by the US, 5, and one each in Canada and Costa Rica.

None of Spain's 100 cases is currently ill enough to be receiving hospital treatment, and all a responding to anti-viral treatment. Spanish health authorities have tested another 162 people with symptoms similar to A/H1N1 flu, who proved not to have the disease.