LONDON - Friday's cyber attack hit 200,000 victims in at least 150 countries and that number could grow when people return to work on Monday, the head of the European Union's police agency said on Sunday.

Cyber security experts say the spread of the virus dubbed WannaCry - "ransomware" which locked up computers in car factories, hospitals, shops and schools in several countries - has slowed, but that any respite might be brief.

Europol Director Rob Wainwright told a British television program the attack was unique in that the ransomware was used in combination with "a worm functionality" so the infection spread automatically.