The virus, which is believed to have originated in Taiwan, was designed to strike on 26 April, the 13th anniversary of the Chernobyl nuclear disaster in Russia.
The virus attacks Windows 95 and Windows 98 programs, attempting to erase the hard-drive and writing gibberish into system settings to prevent the machine from being restarted.
"Arguably, this is the most malicious computer virus ever," said Dan Schrader, director of product marketing at Trend Micro Inc, which manufactures anti-virus software. Other experts disagreed - but many were caught off- guard by the amount of damage caused and said it was much worse than the recent "Melissa" virus. Before it hit, several experts were quoted as saying they did not expect the Chernobyl virus to cause much trouble.
The US suffered far less than other nations, with some 10,000 of the nation's 50 million computers affected, said Roger Thompson, of the International Computer Security Association. Turkey, however, was unprepared, said Mustafa Ucoklar, an electronics engineer. The virus infected computers at banks and an airport and at state-run radio and TV stations, according to Turkey's Radikal newspaper.
In India, at least 10,000 computer owners reported problems. Businesses, banks and publishing houses were shut down and information worth millions of dollars was lost, the Indian Express reported.
Local media reported that up to 10 per cent of all computer users in the United Arab Emirates were affected; at least 10,000 computers were struck in Bangladesh; reports in China varied from 7,600 computers damaged to 100,000.