Thousands of Twitter users on Wednesday reported problems using the platform as the Elon Musk-owned social network began letting paying users post tweets as long as 4,000 characters.

"Twitter may not be working as expected for some of you," the company said in a tweet.

"Sorry for the trouble. We're aware and working to get this fixed."

Reports of Twitter troubles spiked at website Downdetector early afternoon in Silicon Valley, and continued for about two hours.

Users complaints shared online included being unable to post messages, being told they had exceeded a daily limit of tweets, and inability to send direct messages.

A daily limit of 2,400 tweets per day was put in place at Twitter to reduce strain on its operations, according to US media.

People also reported that TweetDeck, the popular dashboard for managing and viewing Twitter accounts, had stopped working.

The disruptions came on the same day Twitter added a length perk to its Blue subscription service costing $8 monthly in the United States.

Twitter Blue subscribers can now post tweets of up to 4,000 characters, far beyond the 280-character limit imposed on non-paying users, the tech firm said.

"But don’t worry, Twitter is still Twitter," the tech firm said in a lengthy tweet announcing the perk.

"We know longer Tweets could mean a lot of scrolling, so they’ll be capped at 280 characters on your timeline and you’ll see a 'Show more' prompt to click and read the whole Tweet."

Musk slashed Twitter's workforce late last year after he became owner of the San Francisco-based company, raising concerns about having enough engineering talent on hand to keep the platform running smoothly.

US tech media reported Wednesday that Musk put out word to Twitter staff to put aside work on new features to focus on troubleshooting.