Twitter said Tuesday it was rolling out tweets which disappear after 24 hours, joining rival social platforms in offering ephemeral messages.

The new "fleets" which had been tested in several countries in recent months are "for sharing momentary thoughts" and aim to bring in users who want to avoid having their comments become permanent fixtures, according to a Twitter blog post.

"Those new to Twitter found fleets to be an easier way to share what's on their mind," said product manager Sam Haveson and design director Joshua Harris in the blog post.

"Because they disappear from view after a day, fleets helped people feel more comfortable sharing personal and casual thoughts, opinions, and feelings."

The move gives Twitter a new tool in competing with the likes of Snapchat, which made disappearing messages popular, and Facebook, which has also adopted the idea.

Twitter has become an important platform for politicians, celebrities and journalists, but it has lagged other social networks in users. 

In the past quarter it reported 187 million "monetizable" daily active users, trailing Snapchat and Facebook.

Twitter said the new format would allow users to create the same kinds messages as in ordinary tweets, including images, videos and emojis, with the option to have the message disappear.

"Your followers can see your fleets at the top of their home timeline," Haveson and Harris said.

"Anyone who can see your full profile can see your fleets there too."

Twitter has been testing the new format in Brazil, Italy, India and South Korea and learned that "we saw people with fleets talk more on Twitter."

Twitter's research director Nikkia Reveillac said the new format was aimed at helping people move from a passive to an active role in the Twitter conversation.

"People must feel comfortable and in control" to participate in the conversation, Reveillac told journalists.

"What we learned when we talk to people is that... engaging in conversation can honestly be incredibly terrifying... And we know that this is true in real life. And we know that it is true online."

Another new feature rolling out to all users is the "voice tweet," or audio recording which takes the place of text and has been tested in the past few months.

"Sometimes, 280 characters just does not cut it," product designer Maya Gold Patterson said.

"And sometimes tweeting isn't the right way of communicating at the moment. And so we were interested in exploring how audio could help add an additional layer to the public conversation."

Patterson said that "hearing the empathy, emotion and nuance in someone's voice could help people connect on a different level" than in a simple text tweet.

She noted that voice tweets may also be used by brands to better connect with customers and by journalists to explain their stories.