A total 29 tyres in the shipment were emitting excess levels of gamma and beta rays, making them unsafe to bring into Russia, a port official said.

"There's a good chance the radioactive tyres are a result of the Fukushima accident," said Ivan Skogorev, a safety inspector.

The tyres' owner might have them decontaminated, shipped backed to Japan or buried in a hazardous waste site in Russia; but as yet the shipment's consignee had not come forward, Skogorev said.

Vladivostok custom officials in April halted a batch of 49 radioactive automobiles exported from Japan, some of which were found to emit dangerous isotopes at six times safe levels. A similar incident was reported in June.

Russia's Far Eastern region is a major consumer of used Japanese automobiles.

Japan's Fukushima nuclear power station suffered a series of nuclear meltdowns as a result of an earthquake.