"We are aware of an iMessage issue caused by a specific series of unicode characters and we will make a fix available in a software update," an Apple spokesperson said in an e-mail.
Sending a reply message or having someone send you a message can solve the problem, MacRumors added.

Apple Inc recently released as OS update for the much-hyped Apple Watch for the improved performance, bug fixes and new language support in less than a month after its release.

According to reports, Watch OS 1.0.1 improves performance for Siri and for health and activity tracking. It also includes display support for new emoji characters and new language support for Brazilian Portuguese, Danish, Dutch, Swedish, Russian, Thai and Turkish.

Apple Inc reportedly showcase its latest mobile operating system iOS 9 for the first time at 'Apple WWDC' scheduled to held from June 8-12.
As per the report, Apple will optimize the new operating systems for improved stability and performance, add several new security features, and make important changes to its Swift programming tools for developers.