SAN FRANCISCO (REUTERS) - Facebook said on Thursday (Sept 21) it plans to share with US congressional investigators some 3,000 political ads that it says Russia-based operatives ran on Facebook in the months before and after last year's US presidential election.

Chief executive Mark Zuckerberg, who has been under pressure to do more to prevent the use of Facebook for election manipulation, said in a live broadcast on Facebook that he supported the investigation by the US Congress.

Zuckerberg laid out nine steps that he said Facebook was taking to deter governments from using the world's largest social network to interfere with elections.

In one major change, Facebook will make political ads on the social network more transparent, so that people can see which ads are being run in connection with an election, he said.

Facebook general counsel Colin Stretch said in a separate blog post that the social network does not disclose content lightly under any circumstances, but that the company wants to help protect the integrity of US elections.

"We believe the public deserves a full accounting of what happened in the 2016 election," Stretch wrote.