UTV News is reporting that Army bomb experts are being sent to the scene of the small explosion in Belfast Cathedral quarter.
There are reports that restaurants and other premises in the area are being evacuated.
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Armed police have taken part in a dramatic training exercise aimed at recreating the chaos of a Paris-style terror attack.
After a remarkably mild November - a notable mild start to the new month.
The Facebook founder revealed the plan as he and wife Priscilla Chan announced the birth of their baby daughter, Max.