Japan's coastguard is to ask for a doubling of its budget to boost patrols around islands that are the focus of a dispute with China, officials said Thursday.

The agency will submit a request to the government for 50.4 billion yen ($485 million) for the financial year starting in April 2015, they said.

The move will come after two years of relentless tensions with Beijing over the Tokyo-controlled Senkaku Islands, which Japan nationalised in September 2012.

That angered China, which claims the chain as its own under the name Diaoyus.

Since the long-simmering dispute flared anew, Chinese vessels and aircraft have regularly approached the unoccupied islands, with Japan's coastguard in pursuit.

The coastguard plans to add one new jet aircraft to its fleet, 10 large patrol ships and four small patrol ships, as well as to increase the number of personnel assigned to the new large patrol ships, it said in a statement.

It will also replace two jets with new ones and retire existing patrol ships in favour of new vessels to boost cruising distance and speed, the officials said.

It also hopes to build a pier, accommodation for crew and other facilities at its base in Ishigaki island, the main jumping off point for the Senkakus.

The measures are part of efforts to push back against Chinese government ships loitering in nearby waters and to create an around-the-clock air patrol system, officials said.

The budget request also considers the "possibility that the number of foreign fishery ships plying disputed waters could double," a coastguard official told reporters.

Aside from Chinese official ships, the number of foreign fishery ships entering the islands' waters has rocketed over the past three years, from 39 over the 12 months to March 2013, to 169 in just five months between April and August this year, the official said.