The device was launched at the Bora Bora nightclub in Caucasia, Bajo Cauca Antioquia, in the early hours of Friday morning.
According to local media, at least 13 people sustained serious injuries as the explosion ripped through the packed venue.
Police said it was launched by a member of the Gulf Clan, one of Colombia’s most powerful crime gang, who fled on a motorbike.
A man and a woman are reported to have been arrested in connection with the incident, but neither have been identified.
Some clubgoers were injured in a stampede as they attempted to leave the scene of the attack.
Mayor Oscar Anibal Suarez condemned the attack as “criminal and shameless”.
The injured are being treated at the César Uribe Piedrahita hospital in this town.
While the investigations are being carried out, the National Police attributed the attack to members of the Gulf Clan
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