A U.S. Coast Guard cutter on routine patrol in the Bering Sea came across several Chinese military ships in international waters but within the U.S. exclusive economic zone, officials said.

The crew detected three vessels approximately 124 miles (200 kilometers) north of the Amchitka Pass in the Aleutian Islands, the Coast Guard said in a statement Wednesday. A short time later, a helicopter aircrew from Coast Guard Air Station Kodiak spotted a fourth ship approximately 84 miles (135 kilometers) north of the Amukta Pass.

All four of the People’s Republic of China vessels were “transiting in international waters but still inside the U.S. Exclusive Economic Zone,” which extends 200 nautical miles (370 kilometers) from the U.S. shoreline, the statement said.

“The Chinese naval presence operated in accordance with international rules and norms,” said Rear Adm. Megan Dean, Seventeenth Coast Guard District commander. “We met presence with presence to ensure there were no disruptions to U.S. interests in the maritime environment around Alaska.”