Beijing is to carry out a geographical survey of islands in the East China Sea, state media said on Tuesday, the latest salvo in an increasingly tense dispute with Tokyo over the uninhabited territory.

The announcement came as Japanese fighter jets were scrambled in response to a Chinese state-owned Y-12 plane flying close to -- but not inside -- the islands' airspace, according to Tokyo's defence ministry.

Separately, official Chinese media reported that Beijing's armed forces have been instructed this year to train for battle, while a Tokyo official said US and Japanese fighter jets carried out joint air exercises.

This week's tensions come after Japan's hawkish Shinzo Abe won a landslide election victory following campaign promises to re-invigorate Tokyo's security alliance with Washington and take a more robust line against Beijing.

The dispute over the islands, known as Diaoyu in Beijing and Senkaku by Tokyo, which controls them, has simmered on and off for years but intensified in 2012 when Japan nationalised those it did not already own, triggering anger and demonstrations in China.

The protests were allowed to take place by the Communist authorities in Beijing, who use nationalism to bolster their claims to legitimacy, particularly regarding Japan, which occupied parts of China in the 20th century.

China has repeatedly sent maritime surveillance ships to the area and carried out naval exercises, and both Tokyo and Beijing have scrambled fighter jets to the area in recent weeks in a further escalation.

Commentators say Beijing wants to prove that Japan does not have effective control over the chain to draw Tokyo into concessions.

The cartographic survey was part of a programme to map China's "territorial islands and reefs" and safeguard its "maritime rights and interests", the official Xinhua news agency said, without saying when it would take place.

It did not make clear whether it would involve activities on land or be purely sea-based, but quoted Zhang Huifeng, of China's National Administration of Surveying, Mapping and Geoinformation, acknowledging there could be "difficulties".

"There are some difficulties in landing on some islands to survey, and in surveying and mapping the surrounding sea area of the islands, because some countries infringed and occupied these islands of China," he said.

Stephanie Kleine-Ahlbrandt, Northeast Asia director at the International Crisis Group, said in an e-mail: "Beijing's goal is to establish as much presence -- if not more than -- Japan in the area to demonstrate its sovereignty.

"A geological survey is another step in this direction. China has made it clear that there is no going back to the status quo in which Japan largely administered the disputed islands on its own."

In September Beijing announced the "base points and baselines of the territorial waters of the Diaoyu Islands", filing details with the United Nations as part of the diplomatic sparring over the issue.

China's State Oceanic Administration also released geographic information including "location maps, three-dimension effect graphs and sketch maps for the Diaoyu Islands", Xinhua added.

While there have been no actual clashes between the two countries' forces in the area, Chinese state media said Beijing's military had been instructed to raise their fighting ability in 2013 and "should focus closely on the objective of being able to fight and win a battle".

Off Japan, six US FA-18 fighters and around 90 American personnel, with four Japanese F-4 jets and an unspecified number of people, carried out joint training exercises in the Pacific, an official said.

The five-day drill followed the nation's first military exercise designed to recapture "a remote island invaded by an enemy force" on Sunday.

In October Japan and the US dropped plans for a joint drill to simulate the retaking of a remote island, reportedly because Tokyo did not wish to provoke Beijing further.