TOKYO: Japan's defense minister on Friday accused two Russian fighter jets of intruding into Japanese air space, heightening regional tensions as Beijing denied Tokyo's claims that Chinese naval vessels had locked their weapons-targeting radar on to a Japanese destroyer last month.

Tokyo said two Russian Su-37 fighters entered Japanese air space off the northern tip of Hokkaido island for just over a minute Thursday, prompting Japanese air force jets to scramble and fly alongside the two Russian planes.

Russia denied any border violation, but Defense Minister Itsunori Onodera said Friday that Tokyo will deal with the incident "strictly, within the bounds of international law."

The alleged intrusion happened when Japan was observing "Northern Territories Day," when it holds annual rallies urging Russia to return a series of islands off eastern Hokkaido captured at the end of World War II. The islands, called the Southern Kurils in Russia, are 400 kilometers (250 miles) southeast of where the alleged intrusion took place.

In Beijing, China's Defense Ministry issued a statement denying Japanese claims that Chinese naval vessels had locked their radar on to a Japanese destroyer and helicopter in two instances last month in the East China Sea.

The countries are embroiled in a territorial spat over a cluster over tiny, uninhabited islands - called Senkaku in Japanese and Diaoyu in Chinese - in the vicinity that are controlled by Japan but also claimed by China and Taiwan.

"The Japanese so-called claims that the Chinese navy locked on to Japanese ships and aircraft with fire control radar are not factual," the Chinese statement said.

It also accused Japan of repeatedly fabricating reports to smear China over the normal training actions of its military and building China up into an international threat.

"The Chinese side wishes that the Japanese side take practical actions, cease creating a tense atmosphere in the East China Sea, and refrain from issuing irresponsible statements," it said.

Japanese Foreign Minister Fumio Kishida rejected Beijing's denial as "completely unacceptable." He told reporters that a thorough review of data by the Defense Ministry confirmed that the Chinese naval ship and locked on with its weapons targeting radar.