Twitter Inc said on Wednesday it would no longer allow people to post identical messages from multiple accounts, cracking down on a tactic that Russian agents and others have allegedly used to make tweets or topics go viral.

The San Francisco-based social network also said it would not allow people to use software to simultaneously perform other actions such as liking or retweeting from multiple accounts.

Twitter, known for freewheeling discussions in short messages, is under pressure from users and Western governments to stem the spread of false news and foreign propaganda, often done with the help of automated accounts known as bots.

Twitter bots disseminated propaganda before the 2016 US elections and have continued to inflame US politics under cover of anonymity, academic researchers and US authorities say.

On Friday, the office of US Special Counsel Robert Mueller charged 13 Russians and three Russian companies, including St Petersburg-based Internet Research Agency known for trolling on social media. The court document said those accused "had a strategic goal to sow discord in the U.S. political system, including the 2016 U.S. presidential election."

Twitter's new restrictions are aimed at improving "information quality," Yoel Roth of the company's policy team said.

"These changes are an important step in ensuring we stay ahead of malicious activity targeting the crucial conversations taking place on Twitter - including elections in the United States and around the world," Roth said in a statement.

Posting identical messages to multiple accounts, or simultaneously retweeting or liking a message from multiple accounts, could help vault something into Twitter's trending list, giving a false impression of how viral it is among real people.

Twitter said it would give users until March 23 to comply before suspending accounts. It made an exception for bots of broad interest such as earthquake alerts.

Twitter has cracked down on other violations of its terms of service, including fake accounts by people inflating their following.

Some US users with conservative politics complained their number of followers had gone down after Twitter asked them to verify their identity. #TwitterLockOut was among the trending topics.

Former Twitter user Jared Taylor, editor of the white supremacist magazine American Renaissance, sued Twitter on Tuesday in state court in San Francisco, saying the decision to ban him violated California law governing "privately owned public forums." Twitter did not respond to a request for comment.

Another company, privately held online publisher Medium, recently removed accounts belonging to far-right US commentators including Mike Cernovich, who said on his Twitter account on Wednesday that Medium was acting unlawfully.

Medium said it would not discuss individual accounts, but a recent rule change banned people from spreading "disinformation."