Crimes by older Japanese people jumped threefold this year compared with a decade ago.

About 45,000 people over 65 were prosecuted between January and November, nearly half of them for shoplifting, the daily Tokyo Shimbun said.

Assaults by older people rose to 1,700 from just 100 in the same period a decade ago, it quoted the National Police Agency as saying.

"Crimes by elderly people are increasing ... faster than the population is ageing," said Osamu Nasu of the Police Policy Research Centre at the National Police Academy.

An increase in the number of isolated older people who do not socialise may be contributing to the rise in crimes, he said.

Japan's population is ageing faster than in any other country, according to a government report in June. About 20 percent of the population was over the age 65 in 2005, and the proportion is expected to double by mid-century, it said.