Ten fire engines and around 70 firefighters have been called to a fire at a shop with flats above on Chalk Farm Road in Camden.
In a statement, the London Fire Brigade said they had been called to the scene just after midday on Friday as temperatures soared in the capital.
Part of the ground floor shop and the roof of a flat on the first floor are alight, the fire brigade said.
Video footage taken at the scene shows the shop engulfed in flames and black smoke billowing from the roof.
Station Commander Brett Loft, who is at the scene, said: “Firefighters are working in incredibly hot and arduous conditions to quickly bring the fire under control.
“There was heavy smoke in the area and local residents were advised to keep their windows and doors closed, but this is now subsiding.
“There are currently no reports of any injuries.”