The San Francisco messaging platform said the move was intended to rid the service of spam-spewing automated accounts, and not aimed at people using the service according to the rules.

"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," Twitter developer policy lead Yoel Roth said in a blog post.

The move was the latest by Twitter to enforce rules aimed at curbing disinformation, propaganda and provocation.

Since the 2016 election, Twitter and others discovered how "bots" had been used to sow political divisions and spread hoaxes.

"One of the most common spam violations we see is the use of multiple accounts and the Twitter developer platform to attempt to artificially amplify or inflate the prominence of certain tweets," Roth wrote.

"To be clear: Twitter prohibits any attempt to use automation for the purposes of posting or disseminating spam, and such behavior may result in enforcement action."

Posting duplicative content, replies, or mentions from an array of accounts one controls, by hand or by bot, is forbidden, according to Twitter.

"Bulk, aggressive, or very high-volume automated retweeting" is also banned, along with using multiple accounts to perform automated actions at the service such as following people, Roth said.

A sole exception to the rule was applications designed to broadcast weather, emergency or other public service type announcements, according to Twitter.

Developers were given until March 23 to bring applications into compliance with the tightened rules or risk suspension.

Keeping Twitter safe and free from spam is a top priority for us," a Twitter spokesperson said.

"Today's update to TweetDeck and our developer platform is an important change to ensure we stay ahead of malicious activity targeting conversations on Twitter."

- Follower counts fall -

The crackdown is part of an effort to weed out automated and fake accounts, a move which rankled some conservative personalities.

Some users woke on Wednesday to find a sharp drop in followers, prompting a series of hashtags on the platform such as #TwitterLockOut and #TwitterPurge.

The cause was an ongoing effort to "identify suspicious account behaviors that indicate automated activity" or other policy violations, a Twitter spokesperson told AFP.

And, despite conspiracy theories that quickly gained traction at Twitter, the service denied any political bias.

"Twitter's tools are apolitical," the spokesperson said.

"This is part of our ongoing, comprehensive efforts to make Twitter safer and healthier for everyone."

Twitter last month said the number of Russia-linked accounts firing off tweets evidently aimed at the US election in 2016 was more widespread than initially determined.

An indictment issued this week by US special counsel Robert Mueller, investigating Russian interference in the 2016 election, named the Internet Research Agency, described as a bot and disinformation operation which sought to sow divisions in American society using social media.