Arsonists have been spotted lighting wildfires by a police helicopter as they continue to dig trenches to protect threatened homes.

The authorities caught the individuals lighting fires near Bolton, as firefighters continued to battle the “major incident wildfire” in the Lancashire moorland that has been raging for the last five days.

Crews remained at Winter Hill, near Bolton, overnight to launch a “large-scale attack” against the “rapidly developing, aggressive fire” which is endangering nearby properties.

While patrolling the area, several people were spotted setting grass alight by Healey Nab in Greater Manchester by a police helicopter.

Tony Crook from Lancashire Fire and Rescue Service said: “As they've been trying to extinguish the fire, people have been seen lighting other grass fires in the vicinity.