"The region's inhabitants are once again reminded that fishing in the Amur is prohibited," the Khabarovsk region's government said in a statement.

In case the ban is extended until summer, the government was prepared to supply fish for the indigenous peoples depending on fishing for their way of life, the statement said, adding that the fish would be then imported from the nearby Chumikan area, northern Okhotsk and the Sakhalin island.

"The pollution levels now registered are safe for humans but dangerous for fish," WWF's Amur program coordinator Nikolai Yefimov explained, adding that "it is not yet clear how nitrobenzene and benzene would affect Amur's fish and other fauna."

However, local experts warned against the move, recalling that up to 10,000 tonnes of fish were caught yearly in the region for personal use.

"The ban will only prompt corruption among officials and inspectors charged with monitoring it, and no one will guarantee that the poisoned fish will not get to people," said the chief of the Pacific fish industry research institute's department in the city of Khabarovsk, German Novomodny.

The toxic slick meanwhile shifted further on, its front edge already 65 kilometers (43 miles) down river from Khabarovsk where "nitrobenzene levels are no higher than 0.28 of the acceptable," the emergency ministry's center said.

The slick has already cleared the village of Novospasskoye some 57 kilometers (38 miles) up river from Khabarovsk, and is due to reach the next major town on the river, Komsomolsk-na-Amure, and its 400,000 inhabitants on January 5 and then flow into the Okhotsk sea.

Much of the benzene that originally entered the river is thought by experts long since to have evaporated.

But nitrobenzene, an oily, colourless or pale yellow liquid with a characteristic smell of bitter almonds whose effects on people range widely from drowsiness to death and which can effect fertility and liver functions, could still be present in high quantities.

The authorities decided Saturday there was no danger to people and the emergency committee handling the crisis was dissolved.

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