China on Tuesday said it warned and monitored a United States Navy warship that entered waters very close to the disputed artificial Spratly Islands. The Guardian reported that China has summoned the US Ambassador after the US challenged the 12-nautical-mile territorial limit set around the islands. The Chinese foreign ministry released a statement saying that the vessel, USS Lassen, “illegally entered” its waters. US officials had not informed China of the mission.

Chinese foreign minister Lu Kang said Beijing would “resolutely respond to any country's deliberately provocative actions” in the South China Sea. China, Vietnam and the Philippines have made overlapping claims on parts of the South China Sea. China’s military build-up in the area is a source of tension between Beijing and the US, but China has said its activities in the South China Sea are aimed at developing infrastructure within its waters.