Japan eyeing Marines, drones in defence paper: reports.

Japan should acquire amphibious units like the US Marines and surveillance drones, newspapers on Thursday reported a government paper will say this week, as a territorial dispute with China rumbles on.

The interim report, to be issued as early as Friday by the Defence Ministry, will also promote "the need to boost a comprehensive capability of containment" as part of anti-ballistic missile measures against North Korea, reports said.

The phraseology falls short of any mention of "pre-emptive strike capability", but reflects an on-going debate in Japan's defence community about the need to re-interpret aspects of the pacifist country's military stance.

Nationalist Prime Minister Shinzo Abe has said Japan needs to discuss the idea of having some kind of first strike provision if it is to effectively counter threats from North Korea's nuclear and missile programmes.

However, observers say he must tread carefully. Japan's constitutionally-prescribed pacifism enjoys wide support in the country at large and is particularly cherished by Abe's coalition partners, a centrist Buddhist party.

The Asahi and Yomiuri, influential papers on the left and the right respectively, say the interim report advocates a US Marines-like amphibious force, capable of conducting landing operations on remote islands.

It also suggests looking at the introduction of a drone reconnaissance fleet that could be used to monitor Japan's far-flung territory.

The report will be reflected in Japan's long-term defence outline that is expected to be published towards the end of this year, a defence ministry spokesman told AFP, adding that a committee comprising top defence officials have been engaged in discussion on these subjects for several months.

China has become increasingly active in the seas surrounding Japan, including waters near the Tokyo-administered Senkaku islands in the East China Sea, which Beijing claims as the Diaoyu islands.

The row over their ownership, which began decades ago, erupted last September when Japan nationalised three of the islands. It took another turn on Wednesday when possibly-armed Chinese coastguard vessels sailed through nearby waters for the first time.

Later in the day Tokyo scrambled fighters to shadow a Chinese reconnaissance aircraft that flew in international airspace in between two Okinawan islands.

It was the first time Beijing had sent a military plane through the gap and out to the Pacific Ocean, Tokyo officials said, adding they saw it as a sign of "China's ever-growing maritime advance".

Abe's administration decided to review the current long-term defence outline which was drafted by the now-opposition Democratic Party of Japan in 2010.

The hawkish premier this year boosted Japan's defence budget for the first time in over a decade against the backdrop of growing concerns among many countries in the region about China.