Facebook said last night that its profit took a hit from setting aside billions of dollars for an anticipated fine from US regulators, in a quarterly report that sent shares higher. 

The leading social network logged a profit of $2.4 billion - down 51% from a year earlier - on revenue that climbed 26% to $15.1 billion in the first three months of this year.

The number of monthly active users of Facebook at the end of March was 2.38 billion, up 8% from a year ago. 

Facebook estimated that it will be hit with a fine of $3 billion to $5 billion by the US Federal Trade Commission for "user data practices," and factored that into its earnings report. 

"The matter remains unresolved, and there can be no assurance as to the timing or the terms of any final outcome," the California-based company said in the release. 

Facebook shares rallied more than 7% in after-hours trade following the results.

Profits would have topped Wall Street forecasts if not for the money put aside for the expected FTC fine.

"We had a good quarter and our business and community continue to grow," Facebook chief executive and co-founder Mark Zuckerberg said in a statement. 

"We are focused on building out our privacy-focused vision for the future of social networking, and working collaboratively to address important issues around the internet," he added. 

The FTC announced last year it was reopening its investigation into Facebook for potential violations of a 2011 settlement over privacy practices.

Over the past year, the social network has come under fire following revelations on the hijacking of personal data of tens of millions of users by Cambridge Analytica, a consultancy working for Donald Trump's 2016 campaign. 

A series of other revelations showed Facebook may have also shared more private data with business partners and advertisers than it had reported, and may have exposed some personal information that should have been secured. 

At the same time, Facebook has been hiring thousands of additional employees to deal with issues such as hate speech, incitement to violence and manipulation aimed at voters.

Facebook said its employee count was 37,773 as of March 31, an increase of 36% over the past year.

Despite the controversies, some 2.7 billion people use at least one of the "family" of the company's applications including the core Facebook network, Instagram, and messaging applications WhatsApp and Messenger.