A dozen environmental activists who cut through a fence to occupy a runway at London's Heathrow airport for several hours have been given suspended sentences.

The 13 members of the Plane Stupid group, which opposes aviation and airport expansion, caused 25 flights to be canceled in July when they got into the restricted airside area at Heathrow and chained themselves to fencing on the runway. They were protesting plans for a third runway at Europe's busiest airport.

The protesters were convicted of trespassing in January and on Wednesday Judge Deborah Wright sentenced each to unpaid community work and six weeks' suspended imprisonment. They were also banned from Heathrow.

The activists' lawyers had argued that they carried out an act of civil disobedience in the public interest.