The US Defense Department charged today that five Chinese ships shadowed and manouvered dangerously close to a US Navy vessel in an apparent attempt to harass the American crew.

Officials in the Obama administration said yesterday's incident followed several days of "increasingly aggressive" acts by Chinese ships in the region. The incident took place in international waters in the South China Sea, about 75 miles (120 kilometers) south of Hainan Island.

US officials said a protest was being delivered to Beijing's military attache at a Pentagon meeting today.

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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 within 25 feet (8 meters), the Defense Department said.

"On March 8, 2009, five Chinese vessels shadowed and aggressively maneuvered in dangerously close proximity to USNS Impeccable, in an apparent coordinated effort to harass the US ocean surveillance ship while it was conducting routine operations in international waters," the Pentagon statement said.

The Chinese ships included a Chinese Navy intelligence collection ship, a Bureau of Maritime Fisheries Patrol Vessel, a State Oceanographic Administration patrol vessel, and two small Chinese-flagged trawlers, officials said.

"The Chinese vessels surrounded USNS Impeccable, two of them closing to within 50 feet (16 meters), waving Chinese flags and telling Impeccable to leave the area," officials said in the statement.

"Because the vessels' intentions were not known, Impeccable sprayed its fire hoses at one of the vessels in order to protect itself," the Defense statement said. "The Chinese crew members disrobed to their underwear and continued closing to within 25 feet (8 meters)."

Impeccable crew radioed to tell the Chinese ships that it was leaving the area and requested a safe path to navigate, the Pentagon said.

But shortly afterward, two of the Chinese ships stopped directly ahead of the Impeccable, forcing it to an emergency stop to avoid collision because the Chinese had dropped pieces of wood in the water directly in front of Impeccable's path.

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"The unprofessional maneuvers by Chinese vessels violated the requirement under international law to operate with due regard for the rights and safety of other lawful users of the ocean," said Marine Maj. Stewart Upton, a Pentagon spokesman.

"We expect Chinese ships to act responsibly and refrain from provocative activities that could lead to miscalculation or a collision at sea, endangering vessels and the lives of US and Chinese mariners," Upton added.

In Beijing, Chinese officials did not immediately respond to voicemail messages and e-mail.

China views almost the entirety of the South China Sea as its territory. China's claims to small islets in the region have put it at odds with five governments — the Philippines, Vietnam, Malaysia, Brunei and Taiwan.

The incident came just a week after China and the US resumed military-to-military consultations following a five-month suspension over US arms sales to Taiwan. And it came as Chinese Foreign Minister Yang Jiechi was due in Washington this week to meet with US officials.

Pentagon officials said the close encounter followed several other incidents involving the Impeccable and another US vessel Wednesday, Thursday and Saturday.

— On Wednesday, a Chinese Bureau of Fisheries Patrol vessel used a high-intensity spotlight to illuminate the ocean surveillance ship USNS Victorious as it operated in the Yellow Sea, about 125 nautical miles (231 kilometers) from China's coast, the Pentagon said. The move was made without notice or warning, US officials said. The next day, a Chinese Y-12 maritime surveillance aircraft conducted 12 fly-bys of Victorious at an altitude of about 400 feet (122 meters) and a range of 500 yards (457 meters).

— On Thursday, a Chinese frigate approached USNS Impeccable without warning and crossed its bow at a close range of approximately 100 yards (90 meters), the Pentagon said. This was followed less than two hours later by a Chinese Y-12 aircraft conducting 11 fly-bys of Impeccable at an altitude of 600 feet (183 meters) and a range from 100 feet-300 feet (30-90 meters). The frigate then closely crossed Impeccable's bow yet again, this time at a range of approximately 400-500 yards (366-457 meters) without rendering courtesy or notice of her intentions.

— On Saturday, a Chinese intelligence collection ship challenged USNS Impeccable over bridge-to-bridge radio, calling her operations illegal and directing Impeccable to leave the area or "suffer the consequences."

Sunday's incident is reminiscent of a similar early foreign policy crisis that forced former President George W. Bush to deal with Beijing shortly after he took office — China's forced landing of a spy plane and seizure of the crew in April 2001.

That incident between a Chinese jet and US Navy spy plane infuriated Defense Secretary Donald H. Rumsfeld, who responded by breaking off US military contacts with China for a time.

The Chinese fighter jet collided in midair with a US Navy EP-3 surveillance plane. The Navy plane was so badly damaged that it made an emergency landing on China's Hainan Island.

The Chinese pilot died and the US crew of 24 was detained by the Chinese military for 11 days. China refused to allow US officials to fix the Navy plane and fly it off the island; eventually it was shipped home in pieces.