Emergency services were called to East Twin Road in the Northern Ireland capital following reports of the blaze. A spokesperson for the Northern Ireland Fire and Rescue Service said crews were on their way to the scene at 1.33pm on Tuesday.
Harbour Police are currently on the scene as large plumes of black smoke can be seen across the city.
An eyewitness told Belfast Live: “Minor bangs and crackles are being heard.”
It is believed the fire is not causing any disruption to the nearby motorway.
Trafficwatch NI tweeted: “#Belfast fire in @BelfastHarbour Estate around Westbank Road / Dargan Road area – smoke visible from M2 citybound around J1 Fortwilliam – not impacting Motorway so far (14:15)”
Footage shared on social media shows towers of black smoke rising up to the sky.
Red and amber flames can be seen inside the smoke as the fire rips through what appears to be storage buildings.
The smoke can be seen for miles as social media users post images of the blaze online.
One person, othernine, tweeted: “What on fire near the docks?
“Can see it from Carnmoney.”
Another person, Andre Colbert, tweeted a picture of the blaze and wrote: “Belfast docks aflame!”
While author D.M Mullan added: “Huge plume of smoke coming from the docks in Belfast.”
Twitter user Colin Jellie tweeted: “Fire at Titanic Quarter.”
More to follow…