By Andrew Hough and Yann Tessier

LONDON (Reuters) - A gunman died when armed police stormed a house in the fashionable Chelsea area of London to end a siege late on Tuesday.

The incident in Markham Square, just off King's Road, began at the start of the evening rush hour and forced the closure of a section of Chelsea's popular shopping street.

Police said the lone gunman had died. They would not say if the injury occurred during three exchanges of fire in an incident lasting five hours or if he had shot himself.

Police had earlier brought in a negotiator to try to talk the gunman out. No hostages were involved.

It is not known what sparked the incident although police ruled out robbery and burglary as a motive.

Witnesses reported seeing the man carrying a shotgun and they said he had fired more than half a dozen shots.

A bus driver told Reuters about eight police cars suddenly appeared as he was travelling down King's Road.

He stopped the bus immediately. "Passengers ran for their lives," he said. "I felt terrified. I immediately thought there was somebody with a gun."

Residents in nearby houses were told to lock their doors and stay away from windows.

Fatalities involving the use of firearms by police must be investigated by the Independent Police Complaints Commission.

The area around King's Road, a fashion centre of London in the 1960s, contains some of the most expensive homes in the capital.

(Editing by Jeremy Lovell and Robert Woodward)