The Philippines' top diplomat warned Thursday that "very threatening" actions from China in staking its claims to contested waters were posing a risk to stability in Asia.

Foreign Secretary Albert del Rosario made the comments following a meeting in Manila with his Japanese counterpart, Fumio Kishida, during which the two sides pledged to deepen security and other ties to counter a rising China.

The Philippines and Japan are locked in separate territorial disputes with China which have simmered for decades but intensified recently amid what the two nations perceive as increasingly aggressive Chinese tactics.

"We talked about the challenges that we appear to be facing in view of the assertions being made by China," del Rosario told reporters.

"I think we all understand that the assertions being made by China, in terms of their nine-dash line claim for example, they do pose threats to the stability of the region."

The so-called "nine-dash" line map lays out China's claims to most of the South China Sea, including waters close to the shores of some of its neighbours.

The Philippines, Vietnam, Malaysia and Brunei, as well as Taiwan, also have overlapping claims to parts of the South China Sea, but China insists it has sovereign rights to nearly all of it.

Del Rosario cited a range of recent Chinese tactics that were of concern to the Philippines, including establishing a local governing authority to rule over the South China Sea and building more infrastructure in contested areas.

"I think these are all very threatening," said del Rosario, who has infuriated China with other outspoken comments. In July last year, he accused China of "duplicity and intimidation" in staking its claims.

Meanwhile, Tokyo is embroiled in an even more hostile dispute with Beijing over a group of uninhabited islands -- known as the Senkakus in Japan and the Diaoyus in China -- in the East China Sea.

Without mentioning China directly, Kishida said the Philippines and Japan needed to boost their ties to help ensure peace in the region.

"As the strategic environment in the region is greatly changing, it is necessary for us foreign ministers to share recognition of the situation," said Kishida, who later on Thursday met Philippine President Benigno Aquino.

Kishida said this also made it necessary to "enhance the strategic partnership between the two countries and cooperate in shaping (a) peaceful and prosperous Asia-Pacific region".

Del Rosario said Japan was committed to boosting the capability of the under-equipped Philippine Coast Guard, which is one of the frontline forces in protecting Filipino interests in the South China Sea.

The Philippines expects to acquire in "about 18 months" 10 new patrol craft from Japan, which will also help train coast guard staff and fund its communications system upgrade to promote maritime safety, he said.

Without making direct mention of the Philippine Coast Guard's requirements, Kishida said: "On the political and security front we agreed on strengthening policy dialogue and enhancing maritime cooperation and other measures."

Del Rosario said that though it was not raised during the Kishida visit, Aquino shared his foreign minister's view that Asia needed a militarily stronger Japan amid an increasingly assertive China.

"I think the president (Aquino) is of the view that a stronger Japan, acting as a counter-balance in the region, would help promote stability for the Asia-Pacific," del Rosario added.