Scotland's fire chief has warned of what he called a "significant increase in self-immolation".

Alasdair Hay, who leads the country's new national rescue service, said he believes around one in four people who die in blazes have taken their own lives.

However, he stressed he did not know if the rise of fire suicides - the figure is still understood to be under 10 - was statistically meaningful or not.

Mr Hay was speaking after it emerged fire deaths fell to their lowest level in two decades in 2013-14, just 33. That compared with 46 the year before and 111 at the turn of the century.

He said: "Around a quarter of last year's fire deaths were suicides. We have never experienced that level previously.

"We are asking questions about mental health and how we can play a part in understanding what is behind that. That work is in its early stages."

The fire chief said that figures could just be a statistical anomaly. Absolute numbers, after all, are low and the "significant increase in self-immolation" could be a simple co-incidence with rare events happening at around he same time.

So Police and NHS have been asked to look at the data to see if there is a trend that needs to be addressed.

Mr Hay, speaking to Holyrood's Justice Committee, said: "We are having conversations with colleagues in health and social care and Police Scotland to see whether there is a pattern in who is committing suicide in that way. Is it a specific group in society?"

Self-immolation is rare form of suicide, meaning numbers are so low it is hard to establish trends.

The number of people who end their own lives has fallen in recent years and stood at 746 in 2013, about a fifth fewer cases than a decade before.

The Scottish Government has invested heavily in its Choose Life programme with self-harm accounted for 10 times as many deaths as homicide and 20 times as many as fires.

Fire - despite a number of recent tragedies, including the killing of Thomas Sharkey and his two children in Helensburgh in 2011 - is also a rare way of killing people.

It accounted for just three per cent of homicides in 2013-2014, according to government statistics.

This January a Belgian woman set herself alight in Clydebank police station. The woman, who was 58, died two weeks later. Her death is being investigated by the Police Investigations and Review Commissioner.