This seems to be a relatively serious escalation in how far the PRC is willing to go:

Philippine supply boats breach a Chinese coast guard blockade in the hotly contested South China Sea

ABOARD BRP CABRA (AP) — As a United States Navy plane circled overhead, two Philippine boats breached a Chinese coast guard blockade in a dangerous confrontation Tuesday in the disputed South China Sea to deliver food and other supplies to Filipino forces guarding a contested shoal.

Two Philippine coast guard vessels escorting the supply boats, however, were blocked by at least four Chinese coast guard ships for about five hours in the tense standoff near Second Thomas Shoal.

One Chinese coast guard ship came as close as 46 meters (50 yards) as it crossed the bow of BRP Cabra to block the Philippine coast guard ship, which maneuvered fast to avoid a collision, said a coast guard officer onboard the Cabra who could not be named because of official policy.

The Cabra and another coast guard ship, the BRP Sindangan, were surrounded by four Chinese coast guard ships and four suspected militia vessels and forced to stop as the other two Philippine boats delivered supplies to the Filipino forces at Second Thomas Shoal, more than 7 kilometers (4 miles) away.