Beijing on Tuesday dismissed an annual Pentagon report that accused it of widespread cyberspying on the US government, rejecting it as an "irresponsible" attempt to drum up fear of China as a military threat.

The paper came as concerns in Washington have grown over Beijing's double-digit rises in defence spending and a steady hacking campaign which the Pentagon says can be traced to the Chinese government and military.

China has repeatedly rejected accusations of online attacks, and said it is committed to a peaceful rise while maintaining the right to defend itself.

The reports were "making irresponsible comments about China's legitimate and normal defence-building and hyping up the so-called idea of a China military threat", foreign ministry spokeswoman Hua Chunying told a regular press briefing.

"This behaviour is not conducive to mutual trust or cooperation," she said. "We express firm opposition to this and have made representations with the US.

"China is committed to a path of peaceful development and pursues a defensive defence policy," she added, saying that "we resolutely oppose any form of hacking attacks".

The Pentagon report, delivered each year to Congress, was the most explicit statement yet from the US that it believes China's cyberspying is focused on the US government as well as on American corporations.

The efforts were intended to "support intelligence collection against the US diplomatic, economic, and defence industrial base sectors that support US national defence programmes", it said.

China in March revealed a 10.7 percent increase in its annual defence spending, taking the official budget to $114 billion, although experts believe the actual figure is much higher.

The Pentagon estimated China's total military spending for 2012 was already well above that, at between $135 billion and $215 billion.

A commentary by the state news agency Xinhua on Tuesday also slammed the report as a "groundless assessment" and "unwise move" that was "harmful to the aspiration of both countries to forge a cooperative partnership.

"China is justified to develop its military capabilities to safeguard its sovereignty and protect its vast interests around the world," it said.