The war in Yugoslavia has spread to the Net with Nato suffering attacks on its computer systems from Serbia, and the UK escalating its propaganda campaign on Thursday through government Websites.

Chris Nuttall reports on the Kosovo infowar

Nato spokesman Jamie Shea apologised at a briefing on Wednesday for the erratic service being provided by its Website. The site, containing information about the bombing campaign including video of air strikes, has often been down or slowed to a crawl since March 28.

"We have looked at this very carefully and it seems that we have been dealing with some hackers in Belgrade who have hacked into our website and caused line saturation of the server by using `ping' bombardment strategy," he said.

As well as stifling Nato's propaganda efforts, Net users opposed to the bombing have also been infiltrating and clogging the defence alliance's computer system.

"It has also been saturated by one individual who is currently sending us 2,000 e-mails a day and we are dealing with macro viruses from Yugoslavia into our e-mail system," said Shea.

These could be similar to the Melissa virus discovered on Friday, and rapidly replicated around the Internet.

Macro viruses reside in Microsoft programs such as Word and Excel and are carried in documents attached to e-mails.

White House attack suspected

In the United States, the Secret Service has been investigating whether a crash experienced by the White House Website at the weekend was the work of Serbian or Russian hackers.

The Russian media has been reporting that the Nato and White House Websites are being targeted by hackers.

It is unclear whether the attacks are state-sponsored or the work of individual groups of hackers. Last October, a group known as Black Hand based in Serbia attacked a Kosovo Albanian Website and threatened to sabotage NATO's site.

A group known as the Beograd hackers have been taking over sites in the past few days and replacing home pages with a "Yugoslav citizens' message to Nato World Criminals". The page features the logo "We are all targets! Stop Nato attack on Yugoslavia."

UK steps up Net propaganda war

Meanwhile, the British Defence Secretary, George Robertson, has announced that the Ministry of Defence Website is offering news on the conflict in Serbian to counter what he said were lies and propaganda from Belgrade.

The MoD site had received 1,400 hits from the Federal Republic of Yugoslavia in 24 hours, he said.

The Foreign Secretary, Robin Cook, announced on Thursday that the government was "stepping up the propaganda war."

Robin Cook: Serbs reading our Websites

"One of the ways in which the Serb people can get the truth that is blocked by Milosevic and his family is through the Internet," he told a briefing.

"Later today, I will be sending a message to the Serbian people via the Foreign Office website explaining what the truth is behind President Milosevic_s atrocities in Kosovo and why we had to act to halt it.

"I have also given an interview to the Serbian independent radio station, B92, which will be broadcast today. That radio station has of course been shut down by President Milosevic."

B92 is continuing to broadcast over the Internet in Serbian and English.

"I bitterly regret having to enter into conflict with your country. It started because President Milosevic chose to ignore our warnings and conduct the most awful cruelty in Kosovo." the Foreign Secretary said in his Internet message.