An advisor to the EU's top court said on Tuesday that Facebook could be ordered to seek out all content on its platform identical to that found to be illegal by a court injunction.

"This case raises important questions about freedom of expression online," the company said in an emailed comment.

"We remove content that breaks the law and our priority is always to keep people on Facebook safe. However this opinion undermines the long-standing principle that one country should not have the right to limit free expression in other countries."