TOKYO, Aug 20, 2012 (AFP) - Police were on Monday interviewing 10 nationalists who raised Japanese flags on an island at the heart of a corrosive territorial row, sparking protests in China.

"They showed up at Yaeyama Police Station at 11am... Interviews of them have started," an official at Okinawa police in Japan's southernmost prefecture told AFP by telephone.

The questioning was being done on a voluntary basis and the local police were trying to "get a handle on what happened", the official said.

The police were examining whether the landing was "appropriate under the law", he said while declining to give further details.

Japanese media said the ten could be charged with a minor offence for landing on the island without proper government permission.

Four members of a local assembly in Okinawa, who landed on the island in January and were questioned by the police, were not charged.

On Sunday members of the right-wing group Gambare Nippon (Hang In There Japan) swam ashore from a 20-boat flotilla carrying activists and lawmakers.

The landing came just days after Tokyo deported pro-Beijing protesters who had landed on the island, part of a chain administered by Japan but claimed by China, which said Sunday's action was illegal.

They had spent around five hours at the islands, known as Senkaku in Japan and Diaoyu in China.

Japanese coastguard ships had urged the activists not to land, with officers boarding some of the vessels to question people. No arrests were made.