The BBC's Ed Mennell: The children would have died if fire crews had not arrived quickly

Staff at the Royal Hospital for Sick Children said the two boys, aged four and one, were critically ill in the intensive care unit.

The Asian youngsters were rushed to hospital on Friday suffering from severe smoke inhalation after being overcome by the fumes when the blaze broke out at teatime in a ground-floor flat in the Leith area of Edinburgh.

The two boys were rescued from the living room by firefighters who braved heat so fierce that it melted their helmets.

The children were given oxygen before being rushed to hospital.

Around 35 firefighters in seven appliances tackled the blaze after arriving to find two adults being beaten back by the flames and thick smoke.

Severe heat damage

Lothian and Borders Fire Brigade assistant divisional officer Brian Chisholm said the fire was believed to have started in the living room of the flat, and might have been caused by an oil lamp. "It wasn't deliberate," he said.

"The seat of the fire was the living room. We know there was an oil lamp of sorts in the living room, and the forensic people are doing a test to find out if that was a contributing factor."

Assistant divisional officer Chisholm said: "It was very very hot. The paint was blistering on the outside of the front door due to the heat. There is a lot of severe heat damage throughout the house."

He added: "It was quite dramatic at the start, but we managed to bring it under control pretty quickly."