Children are putting their lives at risk by playing on the ice covering one of England's largest lakes, police warned.
Youngsters have been seen trying to smash holes with boulders as they play on the ice on Derwentwater in the Lake District.
Two young children were spotted on Saturday, accompanied by their parents, playing on the ice 50ft from the shore, and other youngsters have been spotted on bays and inlets covered with ice.
Derwentwater is one of England's largest lakes, at three miles long and one mile wide.
But it is very shallow, around 75ft deep at its deepest point, with an average depth of around 15ft, making it one of the first lakes to freeze over in the winter.
The cold weather has seen large parts of the lake covered with ice and temperatures are not expected to rise in the next few days - prompting police to issue a warning.
Sgt Garry Armstrong from Keswick Neighbourhood Policing Team at Cumbria Police said: "This is a very dangerous situation and people are putting their lives and potentially the lives of others in real danger.
"There is no uniformity in the formation of the ice and it can become thin very quickly.
"It may appear to be suitable to walk on but you cannot see or gauge the depth of the ice that has formed.
"If someone does happen to fall under the ice with the temperatures we are experiencing the consequences could be fatal.
"What is even more alarming is that children are going out on to the ice carrying large boulders and trying to break it directly beneath where they are standing while parents either go on with them or watch from the lakeside.
"We are urging people not to go out on the ice."
Police were first called on Saturday afternoon to the lakeside at Kettlewell after receiving reports of two young children 50 yards out from the lakeside, playing on the ice and trying to break it up underneath their feet using stones and boulders.
Bordered by woods and towering crags, Derwentwater is hailed as "Queen of the Lakes", and is surrounded by some of the most magnificent scenery in the Lake District.
The police warning in Cumbria comes after a man plunged into a frozen lake in Greater Manchester to save his pet dog.
Walkers in Alkrington Woods, Middleton, watched from dry land as the animal lover waded into the icy waters in subzero temperatures.
He had been shouting at his black cocker spaniel, Jarvis, to come back to the shore after it ran on to the ice to chase ducks.
But the dog became trapped in water which had not frozen over in the centre of the lake and after five minutes of frantic doggy paddling was struggling to keep his head above the surface.
His owner quickly removed some of his clothes and stepped off the bank, smashing the ice as he went neck-deep into water.
Both emerged from the water shivering from the cold but the owner simply shook the water off his clothes and walked away.