The Japanese military scrambled F-15 fighter jets after a Chinese government plane entered the airspace over a set of disputed islands under Japan’s administration in the East China Sea, news agencies reported citing Japan’s foreign ministry.

Japan's chief cabinet secretary, Osama Fujimura, condemned the Chinese intrusion into the airspace claimed by Japan.

“Despite our repeated warnings, Chinese government ships have entered out territorial waters for three days in a row," Fujimura was quoted as saying by Reuters.

"It is extremely regrettable that, on top of that, an intrusion into our airspace has been committed in this way," he said, adding that Japan had formally protested through the diplomatic channels.

The defense ministry said F-15s were headed to the area Thursday morning, but no further action was taken.

Japanese officials later said the Chinese aircraft had left the area.

A defense ministry spokesman told Reuters that this was the first time this year that a Chinese plane intruded into the airspace near the islands.

Tensions between the two Asian powers have been running for decades and escalated Sept.11 when Japan announced the signing of a contract worth 2.05 billion yen ($26 million) to buy three of the five main islands, known as Senkaku in Japan and Diaoyu in China, from their private owner.

The islands, surrounded by an area rich in fisheries and believed to contain significant hydrocarbon resources, have long been a matter of dispute between Tokyo and Beijing.

China have laid claim to the islands since the UN returned them to Japanese sovereignty, in accordance with the Okinawa Reversion Agreement that ended the U.S. occupation of Okinawa. Despite the normalization of relations between China and Japan in September 1972, repeated tussles involving fishing and patrol boats from China, Japan, Taiwan and Hong Kong have occurred in the past.

The airspace intrusion comes ahead of this weekend’s Japanese elections, which might see the return to power of former Prime Minister Shinzo Abe of the centre-right Liberal Democratic Party.

Though Abe had tried to improve Sino-Japanese relations during his earlier premiership, opinion polls have indicated that he is unlikely to take a similar approach if he assumes power this time.

In an interview with the Wall Street Journal in November, Abe stressed his resolve to maintain a tough stance in confronting China with regard to the island dispute.

"What we have now are furious fights between coast guards," Abe had said referring to China’s naval intrusions. "For now, we need to focus on making sure we defend these islands. We need to display our strong resolve and action."

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