Satellites Capture China's Militia Ships Parked in US Ally's Territory

China's maritime militia, comprising hundreds of paramilitary fishing boats across the South China Sea , were seen anchored inside Philippine-held territory this week in a move described by one long-time observer as possibly "unprecedented."

In a satellite image provided by Planet Labs, at least 11 Chinese militia ships could be seen on Monday within Second Thomas Shoal, one of the over 100 islands and reefs in the Spratly Islands archipelago, which is contested by half a dozen nations by claimed strongly by the People's Republic of China .

Over the weekend, the Philippines reported consecutive days of standoffs between its government vessels and China Coast Guard ships, which deployed water cannons and unspecified sonic weapons in a bid to prevent Manila's resupply mission at Second Thomas Shoal on December 10 and at Beijing-controlled Scarborough Shoal the day before.

Both features lie within the Philippines' exclusive economic zone, giving the country a sovereign right to exploit the underwater resources there. Manila said Beijing's territorial assertions violated international maritime law. China said the Philippine boats were trespassing .

China's maritime militia vessels , which took part in efforts to harass and blockade Philippine boats, appeared to remain at Second Thomas Shoal after the confrontation, a departure from the norm, according to an analysis on Thursday by the Stanford-affiliated SeaLight Project.

The militia boats, whose existance isn't officially acknowledged by officials in Beijing, typically leave the area after assisting the Chinese coast guard's blockade, wrote Ray Powell, director of SeaLight.

"This highly unusual invasion of the shoal's interior appears to have been a calculated show of force by Beijing," he wrote. "It's quite rare to see PRC vessels enter the shoal's interior at all, but 11 is certainly the highest number we've yet observed at SeaLight. In fact, it may be unprecedented."

The satellite photograph showed the Chinese hulls dotted across Second Thomas Shoal , including near the BRP Sierra Madre , a rusting Philippine Navy warship deliberately grounded at the north of the territory to serve as Manila's outpost.

Additional open-source analysis by Powell said 26 militia ships and one Chinese coast guard vessel remained outside the shoal, surrounding it.

Photos released by the Philippines armed forces showed a number of the purported fishing vessels still anchored inside the shoal on Thursday.

Vice Adm. Alberto Carlos, chief of Manila's Western Command, told CNN Philippines that five Chinese militia vessels remained inside the shoal, while four militia boats and one China Coast Guard ship were outside.

It remains a tense situation for all regional stakeholders, including the United States, which is treaty-bound to defend the Philippines against an "armed attack," including in the South China Sea. China watchers believe Beijing intends to push the envelope , in part to test American resolve.

In 2012, China's maritime forces wrested de facto control of Scarborough Shoal from the Philippines and have maintained an occupying presence there ever since. Seizing Second Thomas Shoal would not be as straightforward, not least because of the Sierra Madre , which remains in active service.

"I don't believe the PRC will move on the Sierra Madre directly. It has invested many years in its blockade of the outpost, by which it aims to see it disintegrate and be abandoned by its occupants," Powell told Newsweek .

"At that point it can take control of the shoal without directly assaulting a still-commissioned Philippine Navy ship, which would surely constitute an 'armed attack' and trigger Article IV of the Philippines' Mutual Defense Treaty with the U.S.," he said.