CHINA has sent a spy ship to international waters off Hawaii during a US-led naval exercise involving 22 countries, even though Beijing is participating in the drills for the first time this year.

The US Navy played down any intelligence risk associated with the proximity of the Chinese surveillance vessel and noted that China also sent a similar ship to monitor the last Rim of the Pacific (RIMPAC) exercise two years ago.

Captain Darryn James, chief spokesman of the US Pacific Fleet, said: "We've taken all necessary precautions to protect our critical information.

"We expect this ship will remain outside of US territorial seas and not operate in a manner that disrupts the ongoing Rim of the Pacific maritime exercise."

China's Defence Ministry said its naval vessels had the right under international law to operate "in waters outside of other country's territorial waters".