Facebook is banning private gun sales between people on its social network and its Instagram photo-sharing service on Friday, countering concerns that it was increasingly being used to circumvent background checks on gun purchases. Facebook is banning people from arranging deals in private messages, the company said. The company is already bans the sale of illegal drugs.

"This policy update focuses on private or 'peer-to-peer' sales of weapons, not weapons that are being sold in stores or off Facebook through online, licensed retailers," Facebook said in a statement Friday. Licensed firearm retailers will still be able to post about their goods and services on Facebook.

The move comes as the United States debates the issue of access to guns after a string of mass shootings.

Advocacy groups have lobbied Facebook and other online forums to restrict users' posts about firearms for sale on their profiles and group pages. The groups say it enabled illegal sales by failing to police the conversations that led to them.