There has been a large explosion and fire at the site of a major gas pipeline near St Petersburg in Russia.

There were no reports of casualties and officials from the company Gazprom said gas exports were not affected.

Witnesses spoke of a massive explosion that shook buildings 5km from the epicentre and caused traffic jams as people jumped in cars and fled the area.

The explosion took place at a point where the pipeline ran close to a power station on the northern outskirts of St Petersburg.

The cause is not known but the head of the regional emergencies ministry said he did not believe it was a terrorist incident.