US Democratic presidential candidate Hillary Clinton has accused China of stealing commercial secrets and "huge amounts of government information".

Speaking at a campaign event in New Hampshire, Clinton said on Saturday that she wanted to see China's peaceful rise, but warned the US to remain vigilant.

"But we also have to be fully vigilant, China's military is growing very quickly, they're establishing military installations that again threaten countries we have treaties with, like the Philippines because they are building on contested property," said the former secretary of state who served 2009-2013.

"They're also trying to hack into everything that doesn't move in America. Stealing commercial secrets ... from defence contractors, stealing huge amounts of government information, all looking for an advantage," she said.

Clinton's language on China appeared to be far stronger than that usually used by President Barack Obama's Democratic administration.

She is the front-runner to win the Democratic nomination for the November 2016 presidential election.

Asked about the remarks, a White House official declined to comment.

In the most recent case involving suspicions of Chinese hacking, Obama administration officials have said China is the top suspect in the massive hacking of a US government agency that compromised the personnel records of at least 4.2 million current and former government workers.

China has denied hacking into the computers of the US Office of Personnel Management.