The heist happened It happened at Tyndale Drive in the Oldpark area around 9.50 am.
A PSNI spokesman said: “Officers received a report that two men armed with what is believed to be a Taser, approached two postmen and made off with a post van”.
The vehicle was set alight a short time later on Crumlin Road.
Police believe post bags may have been stolen from the van before it was burned.
The postmen were not injured in the incident.
Detectives in north Belfast have appealed for anyone with information about the armed robbery to contact them on the 101 non-emergency number.