The Philippines notified China about a Philippine navy frigate that ran aground in the South China Sea to avoid any misunderstanding because the incident happened near a hotly disputed region, three Philippine officials said Friday.

The BRP Gregorio del Pilar ran aground during a routine patrol Wednesday night in the vicinity of Half Moon Shoal, which is called Hasa Hasa in the Philippines, the Philippine military said, adding that its crew was unhurt.

The barren shoal is on the eastern edge of the disputed Spratly archipelago, where tensions have run high in recent years after China transformed seven disputed reefs into islands, including three with runways, and reportedly installed missile defense system.

The United States and Asian governments which have claims in the region, including the Philippines, raised alarms over China's island building and militarization of the strategic territory.

The Philippines earlier was one of the most vocal critics of China's assertive moves in the disputed waters. In 2016 it largely won a complaint it lodged before an international tribunal, which invalidated Beijing's sweeping territorial claims in the South China Sea. Philippine President Rodrigo Duterte, however, took steps to revive once-frosty ties with China after he took office in 2016 as he sought infrastructure funding and more trade and investment from Beijing.

The three Philippine officials said China was informed of the accident through its military attache at its embassy in Manila. They spoke on condition of anonymity because they weren't authorized to discuss the issue publicly.

Defense Secretary Delfin Lorenzana said China offered to help deal with the problem but that the Philippines can handle it.

"It was not intentional," military spokesman Col. Noel Detoyato said about the grounding, in which he said the frigate hit a shallow stretch of coral outcrop sideways.

Two Philippine tugboats were en route to extricate the frigate, Detoyato said, adding that the military deployed an aircraft to monitor the stalled ship.

A Chinese frigate ran aground on the shoal in 2012 and was pulled away by Chinese military ships.

Half Moon Shoal lies about 110 kilometers (68 miles) from the southern tip of the western Philippine island of Palawan and south of Second Thomas Shoal, where a Philippine navy transport ship was intentionally grounded in 1999 and has since served as a Philippine military outpost.

China has repeatedly demanded the removal of the now rusty BRP Sierra Madre from Second Thomas Shoal, which is claimed by the Philippines and China.

A military report seen by The Associated Press said the propellers of the BRP Gregorio del Pilar, which has more than 100 crewmembers, were damaged by the grounding. The crew checked the frigate after it ran aground and reported that it was not taking in water.

Detoyato said the frigate had minimal hull damage and its engine was running.

The frigate is one of three former U.S. Coast Guard cutters which were acquired by the Philippine military from the United States and now are the Philippines' largest warships.