Facebook must face a class action lawsuit over its use of facial recognition technology, a California judge has ruled.

The lawsuit alleges that Facebook gathered biometric information without users' explicit consent.

It involves the "tag suggestions" technology, which spots users' friends in uploaded photos; the lawsuit says this breaches Illinois state law.

Facebook said the case had no merit and it would fight it vigorously.

On Monday, US District Judge James Donato ruled to certify a class of Facebook users - a key legal hurdle for a class action suit.

The class of people in question is Facebook users "in Illinois for whom Facebook created and stored a face template after June 7, 2011", according to the court order.

In a successful class action suit, any person in that group could be entitled to compensation.

In his order, Judge Donato wrote: "Facebook seems to believe... statutory damages could amount to billions of dollars."

The decision comes days after Facebook CEO Mark Zuckerberg faced intensive questioning by US lawmakers