Twitter has deleted more than 10,000 bot accounts that it says tried to discourage Americans from voting in the midterm elections.
The social media website said the messages posted by the bots were made to look like they had come from Democrats.
Some of the tweets had said men should not vote because doing so would drown out the voices of women, according to sources quoted by Reuters news agency.
A Twitter spokesman said: "We took action on relevant accounts and activity on Twitter."
The action was taken in late September and early October.
Twitter had been made aware of the problem by the Democratic Party, which is hoping to win back the senate and the house of representatives from Donald Trump's Republican Party on 6 November.
The number of accounts deleted is small compared to recent purges, which have numbered in the millions, but it is still a win for the Democratic campaign.
Identifying and reporting the messages is a complicated operation and the Democratic Congressional Campaign Committee has reportedly developed its own system for this.
It was built in part from publicly available tools known as "Hoaxley" and "Botometer" developed by computer researchers at the University of Indiana.
A user can identify automated accounts, also known as bots, and analyse how they spread information.