A vessel under armed guard and loaded with reprocessed nuclear fuel from France arrived at a Japanese port on Thursday, the first such shipment since the Fukushima disaster as utilities lobby to restart their atomic reactors.

The cargo of mixed oxide (MOX), a blend of plutonium and uranium, was offloaded at the Takahama nuclear plant on the western coast of central Japan, after the ship arrived there early in the morning, an AFP journalist said.

The fuel left the French port of Cherbourg in mid April bound for Japan, French nuclear group Areva has said. The vessel was specially fitted to be able to transport nuclear material and was escorted by an armed sister ship.

Its route was not fully disclosed, but the ship was greeted by protesters and national media which captured images of the vessel from land and helicopters overhead.

Huge black barrels, apparently containing the radioactive material, were offloaded by crane as rigid inflatable boats crewed by security personnel buzzed in the background.

While an army of uniformed police and coastguard officers surrounded the cargo ship, dozens of anti-nuclear campaigners voiced their opposition.

"We do not accept MOX fuel," a protester shouted, wearing a full radiation protection suit.

Kansai Electric Power, which runs the power plant, was expected to request the government's permission to restart the Takahama reactors after new nuclear regulations come into force next month.

Residents of areas hosting Japan's atomic reactors are deeply divided over nuclear plants. They are often the backbone of regional economies but the memory of Fukushima remains raw two years after the world's worst nuclear accident in a generation.

Japan has few energy resources of its own and relied on nuclear power for nearly one-third of its domestic electricity needs until the meltdowns at the tsunami-crippled plant.

All but two of the country's 50 nuclear reactors are offline, shuttered for routine safety checks in the aftermath of the disaster and never restarted because of public resistance and new standards.

Uranium reactors produce a mixture of depleted uranium and plutonium as a by-product of fission. These can be re-processed into MOX fuel, which can then be used in other reactors to generate more power.

Japan has built its own nuclear fuel reprocessing plant, in northern Aomori prefecture, but its opening has been delayed by a series of minor accidents and technical problems.

This has left Tokyo dependent on other countries -- namely Britain and France -- to deal with the plutonium it has produced.

Plutonium can be diverted for the manufacture of nuclear weapons, and there are fears that it could fall into the wrong hands and pose a danger from rogue regimes or extremist organisations.

According to a government report to the International Atomic Energy Agency (IAEA), Japan has about 44.3 tonnes of plutonium, of which 35.0 tonnes are held and being processed in France and Britain, and the remaining 9.3 tonnes is stored in Japan.

The MOX fuel was originally due to be shipped back to Japan in the first half of 2011, but the disaster at Fukushima delayed its return and it has been stored in France.

Since coming to power in December last year, pro-business Prime Minister Shinzo Abe has repeatedly spoken of his desire to restart Japan's idle reactors, citing the need to ensure a stable electricity supply for the country's power-hungry industries.