Five Chinese ships harassed and manoeuvred dangerously close to an unarmed US Navy vessel in an attempt to unnerve the American crew, the Pentagon said yesterday.

Defence officials in the Obama Administration said that the incident, which took place on Sunday in international waters, followed several days of “increasingly aggressive” acts by Chinese ships in the region. The incident took place in the South China Sea, 75 miles south of Hainan Island.

The USNS Impeccable sprayed one ship with water from fire hoses to force it away. Despite the force of the water, Chinese crew members stripped to their underwear and continued closing in to within 25 feet, the Pentagon said.

Robert Gibbs, President Obama’s White House spokesman, said that protests had been issued to Beijing and to the Chinese Embassy in Washington. “Our ships operate fairly frequently in international waters where these incidents took place,” he said.

“We are going to continue to operate in these waters and we expect the Chinese to observe the international laws,” he added. The incident comes a week after a visit to Beijing by Hillary Clinton, the US Secretary of State, part of a diplomatic push by the Obama Administration to engage China.

Yang Jiechi, the Chinese Foreign Minister, is also due in Washington this week to meet US officials.

The Chinese ships included a navy intelligence collection ship, a Bureau of Maritime Fisheries patrol vessel, a State Oceanographic Administration patrol vessel, and two small Chinese-flagged trawlers, US officials said. The US crew radioed to tell the Chinese ships that it was leaving the area and requested a safe path to navigate.

Soon afterwards two of the Chinese ships stopped directly ahead of Impeccable, forcing it to an emergency stop to avoid collision because the Chinese had dropped pieces of wood in the water directly in its path.

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