Murder detectives probing a targeted house blaze that killed a grandmother are following a positive line of inquiry.

Catherine Kelly, 71, died after the fire broke out at her home on Kilmaurs Road, Kilmarnock, at around 11.40pm on Saturday.

Ms Kelly was pronounced dead at the scene while a 41-year-old man, believed to be her son, was taken to Crosshouse Hospital with serious injuries.

Another woman, also 41, was in the house but did not need medical treatment.

A number of local residents who tried to extinguish the fire were treated at the scene for smoke inhalation.

Police and the fire service launched a joint investigation to establish the cause of the fire and revealed it was "wilful and deliberate".

Detectives from the force's major investigations team are following a positive line of inquiry in their hunt for the killer.

Detective chief inspector Allan Burton, who is leading the murder investigation, said: "The outbreak of fire within the house on Kilmaurs Road has resulted in the death of an elderly woman.

"Following a joint investigation with our colleagues at the Scottish Fire and Rescue Service, we now know that this was a targeted and deliberate act.

"Local residents are understandably shocked and I would like to acknowledge the bravery of those neighbours and passing motorists who raised the alarm and attempted to do what they could to extinguish the blaze."

He said he wanted to reassure local residents that "all is being done" to trace those responsible.

Mr Burton added: "From when the fire was first reported, there has been a substantial presence by emergency services in the area.

"Specialist forensic staff and detectives remain at the scene as part of the murder investigation.

"Additional uniformed officers are in the area. Please approach those officers with any information of concerns that you have.

"We have spoken with a number of witnesses at this time. I would ask any local residents or passing motorists who have yet to come forward and speak to police, please contact us with any information you may have."

Officers are following a positive line of enquiry in connection with the blaze and a report is being prepared for the procurator fiscal.

Anyone with information is asked to contact the Incident Room at Kilmarnock Police Station on 101.