Hackers broke into Snapchat, the hugely popular mobile app, accessing the phone numbers and usernames of 4.6 million users and publishing them online, tech news website TechCrunch has announced.

The numbers were partially masked when they were briefly published on SnapchatDB.info, and the unidentified hackers told TechCrunch they had done this "to convince the messaging app to beef up its security."

Snapchat, which allows people to send smartphone photos or video snippets timed to self-destruct 10 seconds or less after being opened, has become hugely popular among teenagers who are easing away from Facebook.

But Australian firm Gibson Security warned last week that glitches in the application could be exploited by hackers.

"Our motivation behind the release was to raise the public awareness around the issue," the hackers said in a statement, published on TechCrunch late Wednesday.

"It is understandable that tech startups have limited resources but security and privacy should not be a secondary goal. Security matters as much as user experience does.

"You wouldn't want to eat at a restaurant that spends millions on decoration, but barely anything on cleanliness."

Created by students at Stanford University in 2011, Snapchat reportedly rejected a $3 billion takeover offer from Facebook last year.