China's state media Sunday urged Japan to seek a post-election foreign policy that will improve relations with its neighbours, as Japanese voted in a poll likely to bring in a more hawkish administration.

It came just days after Beijing's latest effort to bolster its claim to disputed islands at the centre of a fierce row with Tokyo, by submitting to the United Nations information on the outer limits of its continental shelf.

The state Xinhua news agency commentary called on whichever party comes out on top to "devise its foreign policy with a long-term and pragmatic" view so Japan can "repair its strained ties with neighbours".

Ties between the Asian giants have soured in recent months due to the row over the East China Sea islands, which are controlled by Tokyo but claimed by Beijing.

Commentators believe the dispute has given a boost to right-wingers in Japan, where the conservative Liberal Democratic Party is expected to defeat the ruling Democratic Party of Japan in Sunday's elections for parliament's lower house.

Shinzo Abe, LDP president and the likely next premier, has said he would take a harder line on foreign policy and revitalise ties with the United States.

The Xinhua commentary cited a "troubling sign" that some Japanese political parties are advocating a hardline over the country's territorial disputes.

"These policies, if carried out, will surely further sour Japan's relations with its neighbors and even increase political and military risks in the region," it said.

China's foreign ministry said Friday that Beijing told the UN in its submission that geographical characteristics "show that the continental shelf of China in the East China Sea extends to the Okinawa Trough, an important geographical unit with remarkable partition."

Such a definition of China's continental shelf would include the disputed islands. Japan's Okinawan islands lie to the east of the trough.

The escalation in the dispute over the uninhabited islands, known as Diaoyu in China and Senkaku in Japan, was triggered when the Japanese government in September purchased some of the islands from the private Japanese owner.

The purchase triggered at times violent anti-Japanese riots in China.

Ships from Japan, China and Taiwan -- which also claims the island -- have engaged in stand-offs and last week Japan scrambled fighter jets after a Chinese state-owned plane flew over the area.