Speculation surrounding the health of President Vladimir Putin of Russia has been stirred again by comments by President Alexsandr Lukoschenko of Belarus.
Mr Lukoschenko said Russia's 'action man' had hurt his back while practising judo.
''He was on the mat and hurt his spine," he said.
The BBC reports there was speculation previously that Mr Putin, 60, had hurt himself during a stunt on 6 September, when he flew a hang-glider alongside some rare Siberian cranes.
He was seen limping, and grimacing, at an APEC summit in Vladivostok three days later.
Now Prime Minister Yoshihiko Noda of Japan has put off a visit to Russia. Mr Noda was quoted by Japanese media as saying he had postponed a planned visit because "President Putin's health condition is bad".
But Mr Putin's spokesman said no definite date had been agreed and denied his work was being affected.
Spokesman Dmitry Peskov told the Itar-Tass news agency no hard date for Mr Noda's visit had been agreed and he might now come to Russia in January.
In a separate interview with Komsomolskaya Pravda, a tabloid newspaper, he said rumours about the president's health had been "blown out of proportion".
"He is working as before, and plans to continue working at the same pace," he said.
"He is also not planning to stop his sports activities, and, as any athlete, he may sometimes have pain in the back, an arm or a leg. This has never affected his work efficiency."
A Japanese government source told AFP news agency that Russian officials had informed their Japanese counterparts that Mr Noda's visit would have to be cancelled due to Mr Putin having an unspecified health problem.