The Philippines said Sunday it would not lodge a diplomatic protest after China extricated a naval frigate from a disputed South China Sea shoal where it had been stranded for four days.

Last week's stranding of the ship on Half Moon shoal, which Manila calls Hasa Hasa, was likely an accident, Foreign Secretary Albert del Rosario said.

"We don't believe that there were ill-intentions that accompanied the presence of that ship in our EEZ (exclusive economic zone)," del Rosario said.

"As far as filing a diplomatic protest is concerned, my stance is that we will probably not do that," he said.

The ship was reportedly on "routine patrol" when it got stranded Wednesday on the shoal, which sits just 60 nautical miles from the western Philippine island of Palawan, within the country's exclusive economic zone (EEZ).

International law defines a country's exclusive economic zone as being up to 200-nautical-miles from its shores.

The Chinese embassy in Manila said the frigate was "refloated successfully" before daybreak Sunday, and del Rosario said he was informed it was already en route back to China.

"We wish its crew a safe voyage back to China," he said.

The shoal is part of the the Spratly Islands -- which the Chinese call Nansha -- a string of atolls and islands straddling vital shipping lanes in the South China Sea believed sitting atop vast mineral deposits.

Apart from the Philippines and China, the Spratlys are claimed in whole or in part by Taiwan and the other Southeast Asian countries of Brunei, Malaysia and Vietnam.

Overlapping claims to the islands have perennially caused tensions among the claimants, with the Philippines and Vietnam recently accusing China of increasingly becoming aggressive in staking its claims.

The dispute also marred an annual meeting of Southeast Asian foreign ministers held in Cambodia last week, where Manila's chief diplomat accused China of "duplicity" and intimidation.

The dispute divided the grouping, with host Cambodia siding with China, thus preventing them from issuing a customary joint statement that summarises achievements and concerns.

But in a marked turn-around of rhetoric Sunday, Philippine Defence Secretary Voltaire Gazmin said the Chinese frigate apparently made a navigational mistake that caused it to run aground.

He said there appeared to be no signs that it was on a mission to intrude in a Philippine claimed area, noting the absence of structures on the shoal.

"It may have been human error. The CO (commanding officer) may have not seen the rocks," he said.

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