Facebook faces up to Belgian $US125m fine

Facebook is being order by a Belgian court to delete all the data it has collected from users visiting thrid party sites.

A Belgian court is threatening Facebook with a fine of up to 100 million euros ($A175 million) if it continues to break privacy laws by tracking people on third party websites.

In a case brought by Belgium's privacy watchdog, the court also ruled on Friday that Facebook had to delete all data it had gathered illegally on Belgian citizens, including people who were not Facebook users themselves.

Facebook, which will be fined 250,000 euros a day or up to 100 million euros if it does not comply with the court's judgement, said in a statement it would appeal the ruling.

"Facebook informs us insufficiently about gathering information about us, the kind of data it collects, what it does with that data and how long it stores it," the court said.

"It also does not gain our consent to collect and store all this information," it added in a statement.

The social media group uses different methods to track the online behaviour of people if they are not on the company's web site by placing cookies and invisible pixels on third party web sites, the court said.