Philippine President Ferdinand Marcos Jr. has ordered his government to strengthen its coordination on maritime security to confront "a range of serious challenges" to territorial integrity and peace, as a dispute with China escalates.

The order, signed on Monday and made public on Sunday, does not mention China but follows a series of bilateral maritime confrontations and mutual accusations over a disputed area of the South China Sea.

Beijing claims almost all of the South China Sea, a conduit for more than $3 trillion of annual ship-borne commerce. China's claims overlap those of the Philippines, Vietnam, Indonesia, Malaysia and Brunei. The Permanent Court of Arbitration in 2016 said China's claims had no legal basis.