"Our specialists will define more precisely what the characteristics of the nuclear contamination in the Sea of Japan are, and they will also hold environmental and seismic monitoring," Putin said at a meeting of the Russian Geographic Society, which he chairs.

"This is a complex expedition which will run in two stages," polar explorer and President Dmitry Medvedev's envoy to the Arctic and Antarctica, Artur Chilingarov, told journalist on the sidelines of the meeting.

The first stage of the expedition will kick off on April 22 and will last for 24 days. The expedition as a whole is expected to last for about four months, Chilingarov said.

"During the first stage, we plan to hold some research stretching from the Kuril Islands to Kamchatka Peninsula," Chilingarov said.

A powerful earthquake and tsunami hit northeastern Japan on March 11 leaving more than 27,000 people dead or missing and disabling the cooling systems of Fukushima 1 Nuclear Power Plant. Radioactive elements were later found in the water, air and food products in some parts of Japan.

Tokyo Electric Power Co. (TEPCO), the operator of Japan's crippled Fukushima, on Friday began dumping bags containing zeolites - which are able to absorb radioactive substances - into the sea.

Meanwhile, 47 Japanese automobiles indicating high levels of radioactivity remain in the port at the Russian Far East City of Vladivostok.

"These cars should undergo decontamination; the cleanup must be held by the port administration. If the decontamination is done successfully, the cars should be allowed in," Russia's chief doctor, Gennady Onishchenko, said.