VLADIVOSTOK, Russia (Kyodo) Russian and Chinese companies agreed earlier this month to launch a joint venture to farm sea cucumbers off one of the Russian-held islands claimed by Japan, one of the participants said Tuesday.

The first revelation of business activity by a company from a third country on the disputed islands just off Hokkaido quickly drew criticism from Japanese officials.

"It's my understanding that the report has not been confirmed, but if it is true, that's incompatible with our country's position," Prime Minister Naoto Kan told reporters.