Beijing branded a new US spending bill barring government purchases of Chinese-made technology "biased" on Thursday, after the two powers clashed over accusations of cyber-hacking.

The bill, signed Tuesday by President Barack Obama, blocked government buying of information technology equipment "produced, manufactured or assembled" by firms "owned, directed or subsidised by the People's Republic of China".

Federal government agencies could buy IT products from China if they passed an official assessment of risks involving "cyber-espionage or sabotage associated with the acquisition of such system", the bill said.

Chinese Foreign Ministry spokesman Hong Lei hit out at the measure at a regular press briefing, saying it "adopts a biased attitude towards Chinese enterprises under the pretext of information security".

The bill "is not conducive to the development of China-US relations," he added.

The US ban follows a war of words between the world's two largest economies over cyber-attacks, after a US research company said last month that a Chinese army unit had stolen "hundreds of terabytes" of data, from mostly US companies.

China dismissed the report as "groundless" and said its defence ministry websites were often subject to hacking attacks originating in the US.

China is the US' largest trading partner in "advanced technology products" selling it $117 billion-worth in 2010 alone, according to the Virginia-based National Science Foundation.

The bill could hurt Chinese exporters of IT equipment such as Lenovo, which sees sales to US government agencies as a major part of its North American growth strategy, reports said.

Quarter of US firms in China face data theft: lobby
Beijing (AFP) March 29, 2013 - Over a quarter of the members of a US business lobby in China have experienced data theft, the group said on Friday, after the two powers engaged in a war of words over state-sponsored hacking attacks.

An American Chamber of Commerce in China survey of its members found 26 percent of respondents said "proprietary data or trade secrets have been breached or stolen from their China operations".

Data theft "poses a substantial obstacle for businesses in China", the Chamber said in a report.

Most businesses said the threat of data theft was "rising or staying the same", threatening the development of cloud computing, an emerging technology which has received a major push from the Chinese government, the report said.

Beijing's foreign ministry, which has repeatedly denied that China engages in hacking, dismissed the report, with spokesman Hong Lei saying: "We oppose the presumption of guilt, without thorough investigation and solid evidence."

He called on the US to stop "politicising the trade issue, and hyping cybersecurity issues".

The report follows a war of words between the world's two largest economies over cyber-attacks, after a US research company said last month that a Chinese army unit had stolen "hundreds of terabytes" of data, from mostly US firms.

China dismissed the report as "groundless" and said its defence ministry websites were often subject to regular hacking attacks originating in the US.

It also labelled as "biased" a US bill blocking government purchases of information technology equipment "produced, manufactured or assembled" by firms "owned, directed or subsidised by the People's Republic of China".