An envoy from Tokyo handed Chinese leader Xi Jinping a personal letter from new Japanese Prime Minister Shinzo Abe on Friday, in a meeting aimed at smoothing relations amid a bitter territorial row.

Natsuo Yamaguchi, head of the New Komeito party, the junior partner in Japan's ruling coalition, is the most senior Japanese parliamentarian to visit China since the long-running row over disputed islands intensified last September.

At the Great Hall of the People in Beijing both sides expressed appreciation for the trip before beginning private talks, and it was not revealed what the letter said.

"Mr Yamaguchi visits China at a period in which Sino-Japanese relations face a special situation. We attach great importance to your visit," said Xi, the head of China's ruling Communist party and the country's president-to-be.

Yamaguchi said he was "incomparably happy" about the meeting.

While he has no official role in the Tokyo government headed by the hawkish Abe, the occasion was a rare positive step as the territorial dispute weighs heavily on relations between the two Asian giants.

Beijing has repeatedly sent ships to waters near the islands since Japan nationalised part of the chain in September, a move that triggered a diplomatic dispute and huge anti-Japan demonstrations across China.

China has also sent air patrols near the Tokyo-controlled islands, known as the Senkakus in Japan but claimed by Beijing as the Diaoyus. The chain could sit atop vast mineral reserves, it is believed.

Earlier this week, Yamaguchi said he hoped to improve ties but that Tokyo had no plans to compromise over the islands.

"I would like to make a step toward opening the door to normalising our relations," he told reporters before his departure.

Regarding the islands, he said: "Our stance is that no territorial problem exists. That's a shared recognition among the government and coalition."