A helicopter has crashed in central London after hitting a crane on top of a tower block by the River Thames.
The stricken aircraft cartwheeled to the ground and exploded into flames before crashing into a street during the rush hour.
Burning wreckage and aviation fuel covered the road as eyewitnesses reported seeing cars on fire and hearing people screaming.
The Metropolitan Police confirmed that the helicopter had come down, while London Fire Brigade said the crash happened near Wandsworth Road in South Lambeth. Fire and rescue services said they were taking "lots of emergency calls" as eyewitnesses described seeing grey smoke towering into the sky, close to Battersea Bridge.
The crane was on top of a building called The Tower, in the St George Wharf development, and is billed to be one of Europe's tallest residential towers. The building is only a few hundred metres from MI6 and is situated on a busy roundabout. London Fire Brigade confirmed that the crane appeared to have been left "in a precarious position".
Some took to Twitter to report details. One said the aircraft appeared to have hit a crane on a newly built tower block on the south bank of the Thames. It crashed close to a railway line and a branch of Sainsbury's.
Video footage shot on a mobile phone showed an entire road blocked by burning wreckage and aviation fuel. The side of a building on one side of the street was also damaged by the flames. Passers-by stood watching as the wreckage burned. A motorcycle was also lying on its side in the road where it was abandoned.
The incident caused gridlock as roads were closed at the height of the rush hour. Vauxhall Underground station, on the Victoria line, was closed, leading to disruption to services on the line. Road congestion spread out from the scene of the crash - reaching Clapham, Kennington, Wandsworth, Lambeth and Battersea.
Visibility was apparently low with London City Airport in Docklands reporting delays. The top of the tower block was obscured by mist.
Paul Ferguson, who was working in an office near the incident, told BBC News: "There was a flash and the helicopter plunged to the ground. It exploded and you can imagine the smoke coming out of it. It was probably heading from the nearby heliport. It may be that on this misty morning the lights on nearby St George's Tower weren't on and it moved and clipped the edge of the crane and lost control." A woman who answered the phone at the London Heliport, in Battersea, would not comment on the fire.