A man was arrested after running onto the runway at London's busy Heathrow airport on Thursday, triggering a major security alert, police said.
"A man ran towards an Emirates flight," a police spokeswoman told AFP, as television pictures showed police vehicles scrambling to deal with the situation. "He has been removed. We believe he was acting alone."
Police said a rucksack had been recovered. BBC cited an eyewitness saying the man scaled the airport's perimeter fence, ran onto the runway and was eventually surrounded by police and police dogs.
There was no immediate sign that the incident was terrorism related. Britain has been under an increased security since the July 7, 2005 suicide bombings which killed 52 people on the London underground. It is the second major security breach at the airport in the space of three weeks.
On February 25, four activists from environmental campaigners Greenpeace staged a protest on top of a parked jet against the planned construction of a new runway.
Today's incident came a day before Queen Elizabeth II is due to open the new Terminal Five (T5) at Heathrow, designed to increase the airport's capacity to some 100 million passengers a year.
Located to the west of London, Heathrow is one of the world's biggest airports, handling over 68 million passengers a year.
Protestors have recently stepped up a campaign against a third runway at the airport, which they say will damage the environment and add to misery for local residents.