Penny Roberts in Swansea: "Neighbours saw smoke billowing from the house"

Police say the two women and two girls were attacked before the house was set alight.

Detectives named the victims as grandmother Doris Dawson, 80, mother Amanda Power, 34, and her two daughters Katie, 10 and Emily, eight.

Detective Superintendent Martyn Lloyd-Evans said: "It is a serious, dreadful murder of a family who have been brutally attacked.

The BBC's Gilbert John: "Police say the killer must have been bloodstained"

"It is important that we get to the bottom of this as soon as possible."

All four victims were unconscious as they were pulled out of the blazing home and attempts to revive them at the roadside were unsuccessful.

Forensic search

Plastic sheeting was erected outside the family home

Police say a number of fires were started in the house in Kelvin Road, Clydach, near Swansea, after the two women and two girls were assaulted.

Det Supt Lloyd-Evans said: "There is a clear sign that an attack took place in the house and there are a number of seats of fire.

"It is my belief that these people have been attacked first and the fire is merely a way to try to conceal what has taken place.

"All four victims have suffered injuries. Whoever has done this would be bloodstained."

One neighbour said she heard shouts coming from the house shortly before the emergency services arrived at 0430BST.

Police have sealed off the road while forensic teams carry out a thorough search of the area for clues.