Tallaght, Dublin: Three siblings killed in 'violent incident'

Twins Chelsea (left) and Christy Cawley died after what gardaí described as a "traumatic" incident

Eight-year-old twins - a boy and a girl - and an 18-year-old woman have died after a "violent incident" at a house in the Republic of Ireland.

Gardaí (Irish police) were called to the scene at the Rossfield estate in Tallaght in south-west Dublin at about 00:30 local time on Sunday.

The victims were twins Christy and Chelsea Cawley and their older sister Lisa Cash.

Their 14-year-old brother is in hospital with serious injuries.

Lisa Cash who died was a sister of twins Christy and Chelsea Cawley

The children's mother, a woman in her 40s who was not injured, has been released from hospital and is being supported by her family, said gardaí.

A man in his early 20s was arrested at the scene and is being held at Tallaght Garda Station.

Gardaí are not looking for anyone else in relation to the incident and believe the people involved are all known to each other.

Detectives described the incident as "violent, challenging and traumatic".

From the scene: BBC News NI correspondent Mark Simpson

Some neighbours spoke of being woken up by the noise of screaming just after midnight.

A fleet of emergency vehicles arrived at the scene in the early hours of the morning.

There was a sense of panic, which quickly turned to shock and grief with news that three young people had died.

As daybreak broke neighbours started leaving flowers at the scene as detectives examined the house and tried to find out exactly what happened.

A message on one bunch of flowers said: "Fly high little angels, our hearts are broken for you all."

Fianna Fáil councillor Charlie O'Connor said the community in Tallaght had been left in shock by what had happened.

"An event like this involving children, two of them very young, will have a deep effect on their peers, where people will go into school in the morning and find that their friends are not there," he said.

"We have to certainly think of the family and offer them deep sympathy.

Neighbours and friends of the family left tributes close to the scene of the incident

"We have to think of the neighbours here, the wider community, the first responders and everybody who is going to be affected by this story."

Irish national broadcaster RTÉ reported that the twins had recently started classes at St Aidan's Senior National School in Tallaght.

In a statement, principal Tomás Hayes said: "As a school, our priority will be to take every step to ensure that the needs of our students and their families are met at this challenging time.

A man, who police say is known to the three people who died, has been arrested

"We will be providing support to pupils and school staff to help them deal with this tragedy and have requested the support of the National Education Psychological Service."

A neighbour told BBC News NI what she had witnessed in the aftermath of the incident.

"I woke up, heard a lot of commotion going on, voices screaming, saw flashing lights everywhere," she said.

Forensic officers were at the scene for much of Sunday

"This was all going on behind my house - it's just scary to think of, it's horrific."

She added: "The kids would always be so nice and friendly, they would all say hello to you."

The scene remains sealed off and a forensic examination has been taking place.

A first-floor window at the house where the incident happened was broken

The Irish Justice Minister Helen McEntee said that the deaths were "so awful and heart-breaking it is difficult to comprehend".

"My thoughts are with the family and the local community as they deal with this unimaginable crime," she posted on Twitter.

"Gardaí and other services are supporting them at this difficult time."