Twitter is up and running for most users after the micro-blogging site was shut down for more than 90 minutes yesterday.

The Twitter shutdown affected users around the world.

Apica, a web performance monitoring company, said Twitter crashed at approximately 4.23pm British Summer Time, returned momentarily around 5:04pm and then crashed again at about 5:15pm.

The site was back online for most users around 5:30pm, though Apica noted that some "users along both coasts continue to experience problems connecting."

As of 6:45pm, Twitter had not disclosed the cause of the outage on its Status Page.

The company, though, did acknowledge that some users are still affected by the outage. "Our engineers are currently working to resolve the issue," it said.

Twitter did not respond to a request for comment on the outage.

Once the site was back online, Twitter users were quick to express their frustration with the outage.

"Twitter, do not crash again, please," wrote @missbanshee. @OwenJones84 tweeted: "Where were you in the Great Twitter Crash of 2012."

And @john_mcguirk joked: "Twitter could have warned me about this outage before I made that sandwich I was so looking forward to tweeting about."

The crash came a day before the opening ceremonies at the Summer Olympics in London, which is expected to be a prime focus on social networks in the coming days.

In fact, Twitter has created a special page to aggregate tweets from Olympic athletes, coaches and their families, along with sports reporters and announcers.

The Twitter.com/#Olympics page went live today.