LONDON (AFP) - Both runways were closed at London's Heathrow airport on Friday, a spokeswoman said, after a British Airways plane reportedly had to make an emergency landing.

"Both runways are currently closed," the spokeswoman told AFP.

"All passengers and crew have been safely evacuated from an aircraft which is on the northern runway.

"The incident involved one plane. Everyone has been safely evacuated."

Smoke was seen emerging from the plane as it tried to take off, according to reports.

Heathrow is one of the busiest international passenger airports in the world.