Japan's hawkish new prime minister took aim at Beijing again Friday, accusing China of deliberately allowing Japanese businesses to suffer in the corrosive row over disputed islands.

The salvo is the latest from nationalist Shinzo Abe since he swept to victory in elections last month and came as he announced a spending splurge, including on military hardware.

It also follows reports that policymakers want next year's defence budget in Japan to rise for the first time in more than a decade, as Asia's two biggest economies continue to face off over the East China Sea.

"For political ends, harming Japanese companies and individuals in China that contribute to the Chinese economy and society -- I want to say it is wrong for a responsible nation state in the international community," Abe told a press conference in Tokyo.

"It not only harms bilateral relations, it has a significantly negative influence on China's economy and its society."

Japan and China are locked in a bitter battle over the sovereignty of the Tokyo-controlled Senkaku islands, which Beijing calls the Diaoyus.

Tokyo's September nationalisation of three of the disputed islands, the seabed of which is believed to harbour valuable minerals, prompted violent rallies across China, with protesters trying to storm diplomatic missions and vandalising Japanese stores, factories and shops selling Japanese-brand goods.

The riots and an unofficial Chinese consumer boycott cost firms more than $100 million, according to one Japanese government estimate.

Analysts noted the apparent unwillingness of Beijing to stop the sometimes violent demonstrations, at a time the Communist Party was managing a delicate power transfer from President Hu Jintao to Xi Jinping.

Commentators said large-scale protests in the country are usually quashed quickly if the government does not approve.

Beijing took umbrage at the island nationalisation, which came just days after Hu spoke with then-Japanese Prime Minister Yoshihiko Noda on the sidelines of an Asia-Pacific summit in Vladivostok.

China has since ramped up its activities around the isles, sending official vessels on dozens of occasions, often inside territorial waters.

On Friday, Japan's coastguard reported maritime surveillance ships were loitering in the so-called "contiguous zone", which sits a little further out.

Also Friday, Japan scrambled at least one fighter jet after a Chinese plane flew close to Japanese airspace, the defence ministry said.

Military aircraft have gone airborne on numerous occasions to counter Chinese state-owned -- but not military -- planes, the defence ministry has said. Airspace was breached once, last month, the first time since at least 1958.

Unconfirmed reports have said there have also been sorties to meet Chinese airforce planes, including on Thursday.

Observers say Beijing, which insists it is just patrolling its own territory, is looking to prove it can come and go around the islands as it pleases.

Abe came to power in December with pledges he would reverse what he said was Noda's pliant conduct in the face of a confident China.

"Regarding Senkaku, there is no change to my position to resolutely protect this water and territory. There is no room for negotiation on this," Abe told the press conference.

But analysts suggest that while Abe's attitude towards China may be more robust than that of his predecessors, it is also a reflection of the two countries' economic mutual dependency.

"Perhaps the undercurrent of the message was that China is a necessary partner for Japan's growth strategy to climb out of deflation," said Takehiko Yamamoto, professor at Waseda University.

"You might say Japan and China are a married couple that cannot divorce. Married couples fight. But after a period of time, they have to face each other."

The spat has left Japan's already well-equipped coastguard in a prime position to bag more funds.

On Friday a spokesman said it was considering creating a team dedicated full-time to the Senkakus, with a report in the Asahi Shimbun saying this could mean as many as 400 officers on 12 patrol ships.