Google said the attacks targeted online critics of the mining

Vietnam has rejected accusations made by Google and McAfee that malicious software had been used to spy on tens of thousands of Vietnamese web users.

The companies said the software had been used to target anti-government blogs and websites.

McAfee said the perpetrators of the attacks "may have some allegiance" to the country's government.

But Foreign Ministry spokeswoman Nguyen Phuong Nga said the accusations were "groundless".

"We have on many occasions clearly expounded our view on issues relating to access to, and use of, information and information technology, including the internet," she told reporters.

"Vietnam law puts in place specific regulations against computer virus and malware, as well as on information security and confidentiality."

Neel Mehta of Google's security team said last month that the spy software had "infected the computers of potentially tens of thousands of users" around the world.

He said the malware installed itself when users downloaded a popular piece of software needed to type Vietnamese characters.

The infected computers were then used to spy on the users or to block other sites "containing messages of political dissent", he said.

Mr Mehta said the attacks were targeted at opponents of bauxite mining in Vietnam, which has attracted criticism over potential environmental damage.

George Kurtz, chief technology officer and executive vice president of McAfee, said the action appeared to be "a politically motivated attack", because of the individuals and organisations affected.

"We believe that the perpetrators may have political motivations and may have some allegiance to the government of the Socialist Republic of Vietnam," he said.

The alleged cyber attacks come amid an ongoing row between China and Google about the censoring of online content.

Google said it would stop censoring its search results after it complained of a "sophisticated cyber attack originating from China" targeting the email accounts of human rights campaigners.