London: A group of climate change activists staged a protest on one of London Heathrow airport`s two runways on Monday, causing minor delays to flights, the police and airport officials said.
"A group of people have breached the airport perimeter fence and are currently staging a protest on the northern runway," the airport said in a statement.
"Both runways are open, although there will still be delays and a few cancellations," it added.
Around a dozen activists from a group called Plane Stupid broke through airport fencing in the early hours of Monday.
"At approximately 3:45 am (0245 GMT) officers were alerted to a number of protesters who had made their way airside at Heathrow Airport," a police spokesman said.
"A small number of these protesters are believed to have chained themselves."
A video uploaded on the Internet showed several activists chained together with a police officer telling them: "You are causing severe disruption and it will be in the millions of pounds because it will take us a while to remove you."
"There are international flights now being diverted," he said.
A government-appointed commission earlier this month recommended building a third runway at Heathrow to increase capacity but the issue divides Conservative Prime Minister David Cameron`s government and has sparked opposition among local residents.
"Building more runways goes against everything we`re being told by scientists and experts on climate change," said Ella Gilbert, one of the protesters.
London`s five airports form the busiest air hub in the world with around 135 million passengers a year.
Heathrow handled 73.4 million passengers in 2014, making it Europe`s biggest airport by passenger traffic.