Arsonists have torched 36 areas of common land and countryside in south Wales during a 30-hour blitz over the weekend.
The fires damaged 56 hectares (138 acres) of grazing land, spreading quickly after the recent dry conditions.
It is believed that no farm animals were injured during the arson attacks but firefighters said the arsonists had shown no regard for livestock or wildlife.
Writing on Twitter, Jennie Griffiths, of South Wales Fire and Rescue Service, confirmed the fires had been started deliberately.
“Over 56 hectares or 138 acres of countryside has been damaged today by deliberate grass fires,’’ she wrote on Sunday (22 March).
Thirty-nine fire engines spent 19 hours tackling the blazes since Saturday morning.
A spokesman for the fire service has now called on members of the public to help stop the fires: “If you see anything suspicious on our mountains today or can provide any information to help us stop these fires please ring 01443 232380”.