BEIJING - China said on Wednesday it was concerned after a standoff in the Yellow Sea between a U.S. Navy surveillance ship and two Chinese fishing vessels, accusing the U.S. vessel of contravening international laws.

The fifth incident of its kind in two months occurred on Friday in international waters about 170 miles from the Chinese mainland when the fishing vessels approached the USNS Victorious, U.S. defense officials said.

The Chinese vessels came within 30 yards (meters) of the Victorious at one point, they said.

But Chinese Foreign Ministry spokesman Ma Zhaoxu said in a statement the ship was operating in China's exclusive economic zone without permission and had violated Chinese and international rules and laws.

We express our concern about this and demand the U.S. side take effective measures to ensure a similar incident does not happen again, Ma said in a brief statement posted on the ministry's website (www.mfa.gov.cn).

The Pentagon, which accused five Chinese fishing vessels of harassing another U.S. surveillance ship in the South China Sea near Hainan island in March, cited the incident as an example of unsafe Chinese seamanship.

Still, Ma's comments were less strident compared with China's anger over the March incident, when Beijing accused the United States of distorting the truth.

Both countries are working closely together to combat the global economic slump and rein in North Korea's nuclear ambitions, and the last spat soon blew over.

The U.S. should make its intention more transparent, said Niu Jun, an international relations professor at Peking University. But the two sides should also have talks on this issue and establish a mechanism to solve it.

The Victorious, a 3,384-ton (3,069-tonne) ocean surveillance ship designed for anti-submarine warfare and underwater mapping, was conducting what the Pentagon called routine operations in the waters between China and the Korean peninsula when the two fishing vessels appeared.

The Victorious operates under the U.S. Navy's Military Sealift Command with a crew of 24 private contractors and eight military personnel, according to a Navy website.

The Pentagon said the intentions of the Chinese fishing vessels remained unknown.

The Victorious sounded an alarm and turned on its fire hoses to ward off the vessels. But they did not withdraw until a Chinese military ship, identified by the Pentagon as WAGOR 17, arrived in response to the American assistance call and shined a light on the fishing vessels.

The Chinese Foreign Ministry's statement made no mention of the Chinese naval ship.

The Pentagon in March accused Chinese vessels of harassing the ocean surveillance ship USNS Impeccable in the South China Sea, about 75 miles south of Hainan Island, the reported site of a Chinese submarine base. [nID:N10526198]

At the time, U.S. officials lodged a protest with Beijing and said Chinese actions in the region were becoming increasingly aggressive.

U.S. Defense Chief Robert Gates later played down the incident by saying he hoped the problem could be addressed through diplomatic exchanges.

China