MANILA - Malaysia has again rejected the Philippines' claim to Sabah and dismissed Manila's "excessive maritime claims" in the disputed Kalayaan Island Group (Spratlys) in the South China Sea, a note verbale submitted before the United Nations showed.

The document, filed by the Permanent Mission of Malaysia to the UN on Friday, is an apparent escalation of a debate fueled by an exchange of tweets between foreign ministers of both sides in July.

It also marks a rare encounter between two Southeast Asian states with conflicting claims in the South China Sea, where the ASEAN, as a bloc, would usually come together on a united front against China, which claims nearly all of the waters.

"The Permanent Mission of Malaysia wishes also to inform the Secretary-General that Malaysia has never recognized the Republic of the Philippines' claim to the Malaysian state of Sabah, formerly known as North Borneo," read the submission.

It was in response to a note verbale the Philippines sent to the UN in March 6, which asserted the country's sovereignty over the Kalayaan Island Group.

The Manila document was an answer to a December 2019 Malaysian submission on the outer limits of the continental shelf beyond 200 nautical miles in the disputed South China Sea.

Under the United Nations Convention on the Law of the Sea (UNCLOS), the area 200 nautical miles (370 kms) from a country's territorial sea baseline is its exclusive economic zone, where it may exercise sovereign rights to use natural resources and jurisdiction to put up installations or structures.

The law states that "the exclusive economic zone shall not extend beyond 200 nautical miles from the baselines from which the breadth of the territorial sea is measured."

The Philippines' March note said Malaysia's submission on the continental shelf beyond this measure is "projected from portions of North Borneo over which the Republic of the Philippines has never relinquished its sovereignty."

Malaysia has, for long, governed Sabah, while the Philippines has laid a dormant claim.

In its note, Kuala Lumpur cited an October 2001 judgment of the International Court of Justice on the Philippine Claim.

A separate opinion by Judge Thomas Franck upheld the right of the people of North Borneo to self-determination, saying "modern international law does not recognize the survival of a right of sovereignty based solely on historic title."

"In light of the clear exercise by the people of North Borneo of their right to self-determination, it cannot matter whether this Court, in any interpretation it might give to any historic instrument or efficacy, sustains or not the Philippines claim to historic title," read the opinion, which Malaysia cited in its submission.

"In light of the above, the Republic of the Philippines' claim to North Borneo clearly has no basis under international law," the Malaysian missive read.

It also rejected Manila's claims to the Kalayaan Island Group, calling it "excessive." It said the Philippines' assertion also has "no basis under international law."

Instead, it reiterated that its submission was aligned with its "rights and obligations for the delineation of the outer limits of its continental shelf where that shelf extends beyond 200 nautical miles from the baselines from which the breadth of the territorial sea," citing UNCLOS.

Competing claims between the Philippines and Malaysia over Sabah was brought to the spotlight in July after Foreign Affairs Secretary Teodoro Locsin tweeted "Sabah is not in Malaysia," prompting a retort from Malaysian Foreign Affairs Minister Hishammuddin Hussein, who called this "an irresponsible statement."

Both sides then summoned each other's envoys.

• Malaysia to summon PH envoy over Locsin's 'Sabah is not in Malaysia' tweet
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The Philippines lays claim over Sabah citing a land lease agreement in 1878 between the Sultanate of Sulu and the British North Borneo Chartered Co.

There had only been intermittent discussions between the Philippines and Malaysia over the claim, and the latter has continued to govern the territory. In November 2016, Duterte and then Prime Minister Najib Razak agreed to set aside the dispute.

Just last year, on a visit to Manila, then Prime Minister Mahathir Mohamad said "there is no claim" when asked of the Philippines' assertion of sovereignty over Sabah in an exclusive interview with ABS-CBN News.

In response, the Philippines asserted its claim.

In 2013, hundreds of militants from Tawi-Tawi went to Lahad Datu in Sabah to assert their claim, calling themselves "Royal Security Forces of the Sultanate of Sulu and North Borneo.”

Malaysia has sentenced 9 Filipinos to death over the incident.

In 1968, Republic Act 5446 or the law on Philippine baselines included "the territory of Sabah, situated in North Borneo, over which the Republic of the Philippines has acquired dominion and sovereignty."

It was amended in 2009, but a Supreme Court decision said Republic 9522 or Baselines Law still did not relinquish the Philippine claim to Sabah, a claim Malaysia has rejected.