Facebook said yesterday it is investigating reports that some members of the social network were receiving graphic images in their news feeds.

“Protecting the people who use Facebook from spam and malicious content is a top priority for us and we are always working to improve our systems to isolate and remove material that violates our terms. We have recently experienced an increase in reports and we are investigating and addressing the issue,” Facebook said in a statement.

Graham Cluley of computer security firm Sophos said in a blog post that the images appearing in the news feeds of some Facebook users included “explicit hardcore porn images” and “pictures of extreme violence.”

“It seems highly offensive spam content has successfully spread via Facebook for 24 hours or more,” Mr Cluley said, adding that it not immediately clear how it was being spread. “What’s clear, however, is that mischief-makers are upsetting many Facebook users and making the social networking site far from a family-friendly place,” he said.

A number of Facebook users took to Twitter to complain that their news feeds had been invaded by pornographic and violent images.

Facebook is the world’s largest social network.