Feature in Brazil, Italy, India, and South Korea.
"Some of you tell us that Tweeting is uncomfortable because it feels so public, so permanent, and like there's so much pressure to rack up retweets and likes," design director Joshua Harris and product manager Sam Haveson said in a blog post.
"Because they disappear from view after a day, fleets helped people feel more comfortable sharing personal and casual thoughts, opinions, and feelings," they added.
Fleets, which include text, photos and videos, will be available at the top of users' home timelines on Twitter and on the sender's profile.
Twitter and other major social media companies are under pressure to better police abuses and viral misinformation on their sites. Twitter spokeswoman Liz Kelley said fleets are subject to the same rules as tweets.
Kelley also said that warnings or labels, which Twitter has started applying to content such as manipulated media and misinformation about civic processes or Covid-19, could be applied to fleets.
Twitter also confirmed it was working on a live audio feature, dubbed 'Spaces,' that it aims to test later this year. The feature will allow users to talk in public, group conversations. It has similarities with Clubhouse, a social platform in which users are invited to talk in voice chat rooms.
"Given all of the potential for abuse within audio spaces, we are going to be making it available first to women and historically marginalized communities," said Twitter's Kelley.
The company earlier this year launched a feature for users to tweet recorded voice notes.