ARLINGTON, Va. — Two Chinese fishing vessels came "within yards" of a U.S. surveillance ship operating roughly 170 miles off the coast of China in the Yellow Sea on Friday, only relenting when the Americans called a nearby Chinese military ship for help.

According to Pentagon spokesman Bryan Whitman, the double-hulled, 235-foot USNS Victorious sounded alarms and took evasive maneuvers but the fishing vessels did not relent.

The Victorious then called for help via bridge radio with a nearby Chinese military ship, the WAGOR 17.

The Chinese approached one of the fishing vessels and shined a light on it, after which both fishing vessels pulled away from the Victorious.

The Victorious thanked the Chinese and had no further communications, according to a Pentagon statement.

"This was clearly, well into international waters" Whitman said, but would not say what Victorious was doing in the area, only that it was "conducting routine operations."

On March 8, five Chinese vessels, including a Chinese naval intelligence ship, harassed the USNS Impeccable operating 75 miles south of Hainan Island, dropping pieces of wood in its path and trying to snare the Impeccable’s dragging sonar cable while crews waved Chinese flags.

The Pentagon later said the Victorious also was lit by high-intensity lights from a Chinese patrol boat around this time and a Chinese Y-12 surveillance aircraft buzzed the ship a dozen times.

Whitman called Friday’s episode an "isolated incident" and said the intent of the fishing vessels or their crews has not been determined.

"What is clear is that it is unsafe and dangerous behavior and it needs to be addressed," he said. The Pentagon would seek to refer the incident to "proper authorities."

"We’re exploring way to handle this diplomatically," he said.

The 20-year-old Victorious, one of five ocean surveillance ships in the Military Sealift Command, carries eight military personnel and 24 contracted mariners and other workers, according to the command’s Web site.