A “multiple murder” investigation has begun after four people, including two children, died in an arson attack on their family home in County Waterford.

Gardaí (Irish police) confirmed that a man, a woman and two of their children died in the fire at a house on Birch Avenue, on the outskirts of Waterford city.

The parents have been named locally as Philip and Kim English.

Two more of their children are critically injured in hospital as a result of the blaze which was reported shortly after 05:00 local time on Tuesday.

Addressing the media outside Waterford Garda Station on Tuesday afternoon, Ch Supt Anthony Pettit said officers believe the house “was attacked by a person or persons unknown and that the fire was started deliberately”.

“The house at Birch Avenue has been declared a crime scene and is currently subject to a technical examination by the Garda Technical Bureau,” he added.

The officer said the four bodies have been removed from the scene and post-mortem examinations would be carried out at University Hospital Waterford.

The two injured children are being treated at a hospital in Dublin.

Firefighters, ambulance staff and gardaí all responded to the emergency at the family home in the Birchwood housing estate, about 3km (1.8 miles) outside Waterford city centre.

Waterford Fire Service said it was alerted to the fire at 05:13 local time and its crews arrived to a well-developed fire at a two-storey house.

It said a number of casualties were removed from the house before the blaze was extinguished and the scene was handed over to gardaí.

A senior investigating officer is leading the murder inquiry, which is being coordinated from an incident room at Waterford Garda Station.

Family liaison officers have also been appointed to the bereaved family.

Addressing reporters, Ch Supt Pettit appealed for witnesses to what he described as a “multiple murder and arson attack”.

“In particular gardaí wish to speak to anyone who was in the vicinity of Birch Avenue, Birchwood, between 04.30am and 05.30am this morning,” he said.

“Gardaí are also appealing to anyone who was driving in the vicinity of Birchwood, or the adjoining roads, between 4.30am and 5.30am this morning, who may have dashcam footage or images to make such footage available.”

Justice Minister Jim O’Callaghan has described the arson attack as a “brutal and heinous act” and insisted those responsible would “face the full rigour of the law”.

“This shocking event has had a very significant impact not just on the people of Waterford but on the whole country,” he said.

“There is no place in a civilised society for such a heinous act of violence.”

O’Callaghan said the murder inquiry was being supported by the National Bureau for Criminal Investigation.

He expressed his condolences to the family and friends of the bereaved and to the two children in hospital.

The housing estate is just off the Killure Road on the outer edge of the city.

Sinn Féin’s David Cullinane, who represents Waterford in the Dáil (Irish Parliament), said he knew the family and said his heart went out to their relatives.

“I’m just utterly heartbroken,” Cullinane said.

“There is such devastation in the housing estate itself but also in the wider community in Waterford city.”

His party colleague, Sinn Féin councillor John Hearne, also knows the family and described it as a “terrible tragedy”.

Hearne told BBC News NI that residents living in the estate noticed the blaze at about 05:00 and they went out to wake up their neighbours to try to help.

But he said it “all happened so fast” and was “hugely distressing for everyone involved”.

The councillor said the estate had been blocked off by gardaí but he planned to go to the community centre later where the council had set up a support hub.

Waterford City and County Council said facilities and refreshments were available at Butler Community Centre in St John’s Park for anyone affected by the fire.

The Bishop of Waterford and Lismore, Alphonsus Cullinan, described it as an “unspeakable tragedy” which had shocked the entire city.

In a statement, he said: “Our hearts go out to the families who have suffered such unimaginable loss.

“We stand in solidarity with all those whose lives have been devastated”, he added.

He said the Catholic Church would “reach out as best we can” to help those affected and the parish priest would minister to the bereaved family and support the local community.

“We also wish to express our sincere gratitude to the emergency services, gardaí, firefighters and medical personnel who responded to the scene and who have faced such distressing circumstances,” the bishop added.

Local parish priest, Father Gerry Chestnutt, said the family will be supported by the community.

“Some of the children went to our primary schools so they will have lots of friends and parents, they will rally around, while this is a big parish, around this area is very tight knit,” he told RTÉ.

The mayor of the Waterford Metropolitan District, Lola O’Sullivan, urged people not to speculate about the cause of the fire.

“It upsets me no end to see people commenting on social media about something that they don’t have firm facts on,” she said.