TOKYO, July 21, 2008 (AFP) - Political tension, air pollution and concern over food safety in China are cited as some of the reasons behind an influx of Olympians into Japan for training camps ahead of the Beijing Games.

Nearly 1,000 athletes, coaches, trainers and officials from at least 25 nations are descending on Japan to fine-tune their Olympic preparations in dozens of locations -- not in China, a few hours' flight away.

'I hear that the number is still growing even in places we don't know,' said Kenji Nishimura, deputy chief of international affairs at the Japanese Olympic Committee (JOC).

He attributed the convenience and geographical proximity of facilities in Japan for the popularity. For similar reasons, hundreds of foreign Olympians also also training in neighbouring South Korea at the same time.

Greek rowers and Egyptian wrestlers are already working out in Hanamaki, northern Japan, and Tokyo.

Some 70 Swedish athletes in 11 sports, including Olympic and world heptathlon champion Carolina Kluft, arrive in the southern port of Fukuoka on July 22. They are accompanied by some 70 coaches, trainers and officials.

Olympic and world pole vault champion Yelena Isinbayeva of Russia, who upped her own world record by two centimetres to 5.03 metres this month, and dozens of Dutch track-and-field stars will join the Swedes in Fukuoka, the venue of the 1995 World Student Games.

But for five French track-and-field athletes, including 400-metre sprinter Leslie Djhone, Wakayama was not the original venue for their last pre-Olympic training camp August 8-13.

Anti-French activities in China following France's protests against a Chinese crackdown on unrest in Tibet in March forced the French athletic federation to switch the venue from the bustling Chinese city of Shanghai.

'The political tension has led the French athletics federation to assume it would be better to shun China for the training camp,' said Kimihiko Tsujioka, a sports promotion official at the Wakayama municipal office.

'They were worried about air pollution and the safety of food in China,' added an official in Kaminoyama where two athletes from oil-rich Bahrain -- Ethiopian-born world women's 1,500m champion Maryam Yusuf Jamal and Kenyan-born men's 800-metre runner Yusuf Saad Kamel -- will train from August 6-17.

An athletic squad from Bahrain also trained in the city, which has hills at about 1,000 metres (3,280 feet), just before the Osaka world championships last year.

'They also feel it difficult to train in a hot environment in Beijing. The temperature rises to only 22-23 degrees Celsius (71.6-73.4 F) even in the summer in the hills here,' said the offical, Yutaka Sakurai.

The mercury is expected to soar past 35 degrees C (95 F) in Beijing.

Dozens of British swimmers and officials will base themselves in Osaka for a week from late July.

'I understand they have chosen Osaka as they care about food and the environment,' said Masakazu Okumura, the chief secretary of the Osaka Swimming Association.

'One British official showed us pictures of stadia in Beijing shrouded in a haze. He said visibility is poor over there,' he said.

A Fukuoka municipal sports official, Kikuhiro Takenaka, said the Swedish and Dutch teams had picked his city for its abundance of sports facilities and the presence of an airport with daily flights to Beijing.

Nishimura, the JOC official, said it is natural for Olympic teams to train somewhere else in the run-up to the Games because there is limited time and space for training in the host country.

Athletes from more than 30 countries trained in Japan ahead of the 1988 Seoul Games, the last Summer Olympics held in Asia.

'It was the time when people shunned direct flights to Seoul following Korean plane crashes in the 1980's. They tended to stop over in Japan for a few days of training and adapting to time differences,' he said.

In 1983, a Korean Boeing 747 from Anchorage was shot down by a Soviet fighter when it strayed into Soviet airspace over Sakhalin.

A Korean Boeing 707 was blown up by bombs planted by North Korean spies over the Bay of Bengal in 1987.