Media playback is unsupported on your device Media caption Chuck Hagel blames China for some "cyber intrusions"

The US defence secretary has accused China of "cyber intrusions", in one of the most direct rebukes from the US.

Chuck Hagel reiterated concern over the threat of cyber attacks before adding: "Some of which appear to be tied to the Chinese government and military."

He was speaking at a conference in Singapore, attended by a high-level Chinese military delegation.

The US and China have been embroiled in a war of words over cyber security for several years.

Officials from both countries talk frequently of the threat of cyber attacks and accuse each other of involvement.

They also stress that the US and China must work together.

Mr Hagel's speech, at the Shangri-La dialogue in Singapore, followed the same pattern.

Just after chiding China, he said: "We are determined to work more vigorously with China and other partners to establish international norms of responsible behaviour in cyberspace."

Earlier this week US media published details of a leaked Pentagon report that claimed Chinese hackers had accessed secret US weapons programmes.

The report said: "China is using its computer network exploitation capability to support intelligence collection against the US diplomatic, economic, and defence industrial base sectors."

The Chinese military said in a statement that there were "misjudgements" in the allegations.

"First they underestimate the security defence capabilities of the Pentagon, and second they underestimate the intelligence of the Chinese people," said the statement, attributed to national defence spokesman Geng Yansheng.

"China is fully capable of building the weapons and equipment needed to defend national security."