Six People’s Liberation Army Navy (PLAN) frigates and two support vessels were spotted escorting a Chinese aircraft carrier navigating within the country’s territorial waters in Northern Luzon amid the ongoing Philippines-United States Balikatan Exercises.

In an ambush interview in Manila on Thursday, Navy spokesperson Rear Admiral Roy Vincent Trinidad said the Chinese aircraft carrier Shandong (CV-17) was first detected transiting 101.3 nautical miles (NM) northwest of Burgos, Ilocos Norte.

Trinidad said the carrier battle group Shandong was later monitored being escorted by six warships, destroyers and frigates, and two surveillance vessels.

"This is one of the larger or unusual formations we have monitored, considering that we have tracked the aircraft carrier with six warships destroyers and frigates escorting her and two support vessels," Trinidad told reporters.

Trinidad said a surveillance ship is “usually characterized generally as a support vessel.”

“So a support vessel could be a surveillance ship, it could be a research vessel, it could be a replenishment oiler. So they are generally support vessels and warships or escorts,” he added.

Meanwhile, Trinidad said the carrier’s closest point to the Philippine coast was logged at 2.23 NM off Babuyan Island.

Despite this, Trinidad explained foreign vessels are entitled to innocent passage under international law and the United Nations Convention on the Law of the Sea (UNCLOS).

“This is quite close but these are allowed under UNCLOS under the right of innocent passage provided that it is continuous and expeditious,” he said.

However, these vessels will be subjected to radio challenges when they transit nearer to the Philippine archipelagic waters or the country’s exclusive economic zone (EEZ).

Trinidad said the Philippine Navy has repeatedly radio challenged the carrier and its escorts, “but they did not respond.”

“We always challenge foreign warships passing through our territorial waters to our EEZ. This time we didn't get any reply,” Trinidad said.

“While the normal procedure is for warship or foreign ship to reply, there are some instances na hindi sumasagot ang mga ito. This is one particular instance that the Shandong carrier battle group did not give any reply at the moment it was challenged,” he added.

The most recent confirmed position of Shandong (CV-17) was at roughly 180 NM east of Aparri, Cagayan as of Wednesday evening.

“These are usually operating out of the South Sea Fleet. But we didn't notice where it came from,” Trinidad said.

Asked if the carrier’s presence relates to the ongoing Manila-Washington war games, Trinidad replied, “We do not give any correlation or any meaning. What we do is we monitor and we challenge and we respond as necessary.”

“Again, we do not speculate on the intention of their warships in our waters, what we do is we challenge them, we monitor them, to ensure that they traverse continuously and expeditiously,” he added.

Trinidad said the presence of Chinese vessels within Philippine territorial waters is not considered alarming.

“We know they are there, we monitor them, we challenge them, we are aware of their presence,” he said.