One person was injured, and several buildings were extensively damaged by an explosion in Athens early on Wednesday that sparked a fire and wrecked building fronts along a major street in the city center, officials and witnesses said.

One person who suffered burns was taken to hospital, Giorgos Mathiopoulos, the head of workers at the National Center for Emergency Care, told Greece's Skai TV.

Officials said it was not immediately clear what triggered the blast or the fire.

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The explosion smashed windows and wrecked the facades of buildings and shops along the Syngrou Avenue traffic artery, which links the center of the Greek capital to the southern suburbs, while damaging structures up to 200 meters away.

Debris and broken glass littered the street a day after a severe snowstorm swept the city, disrupting traffic and stranding thousands of people.

"At the time of the explosion, I was exactly across from the building. It was strong, really strong, [you see] the buildings around it," said taxi driver Christos Chalkias. His vehicle's windows were cracked.

"The explosion sent us two lanes to the right," he said.

At least 18 firefighters used seven engines to battle a blaze at one building and had nearly brought it under control, the fire brigade said.

"We have a fire. There was a blast before that," said a fire brigade commander at the scene.

The crime investigation unit had also arrived at the scene.