The device exploded outside the door of a property in the Carlisle Square area s hortly before 10.50pm last night.
Police said a man in his 20s who was inside at the time was not hurt but was left badly shaken.
Damage was caused to the doorway in the incident.
Officers said a motive for the attack has not yet been established.
They appealed for witnesses to come forward.
COMMENT RULES: Comments that are judged to be defamatory, abusive or in bad taste are not acceptable and contributors who consistently fall below certain criteria will be permanently blacklisted. The moderator will not enter into debate with individual contributors and the moderator’s decision is final. It is Belfast Telegraph policy to close comments on court cases, tribunals and active legal investigations. We may also close comments on articles which are being targeted for abuse. Problems with commenting? email@example.com