A High Court judge has asked for public help finding four children "abducted" by their mother following a care dispute.
Mr Justice Roderic Wood said he was "very concerned" for Jessica, Tomas, Eva and David Palacin Jones.
(From left) Eva, Tomas, Jessica, David and Sarah (who is not missing) Palacin Jones in a family holiday photo
He said the "vulnerable" youngsters - aged between 14 and eight - had gone missing from their mother Jennifer Jones' house in Llanelli, Carmarthenshire, and "must be found".
The children had been in the care of their Spanish father Tomas Palacin Cambra, 52, who lives in Majorca, said the judge.
Ms Jones, 46, who teaches English as a second language, had "abducted" the children then "defied" a High Court order to return them to her divorced husband, he added.
Mr Justice Roderic Wood said he had ordered the children's "immediate removal" from their mother at a High Court hearing on Monday.
Tomas Palacin Cambra at the back with his children (from left), Sarah (who is not missing), Eva, Tomas, Jessica and David Palacin Jones
But police had found them gone when they went to Ms Jones' home early on Tuesday.
"I am very concerned about the children," said the judge, at a hearing in the Family Division of the High Court in London.
"They must be found. I ask anyone who knows where they are or might have seen them to tell this court or the local police."
He added: "All these children are now missing. The mother removed them from her home in the middle of the night. Her and her children's whereabouts are unknown. I do not know the mother's intentions."
The judge ruled that Jessica 14, Tomas 12, Eva, nine and David, eight, could be identified.
And he authorised solicitors from London law firm Dawson Cornwell, which represents Mr Palacin Cambra, to release photographs.
Jennifer Jones with two of her children, Eva and Jessica Palacin Jones
Dawson Cornwell released photographs of the children with their 16-year-old sister Sara, who, they said, looked like her mother.
Lawyers said Ms Jones and the children were thought to be with her partner, John Williams.
They said Ms Jones spoke with a strong Welsh accent and was slim, about 5ft 7in, with strawberry blonde wavy hair and brown eyes.
Mr Williams was said to be in his late 40s or 50s, taller than Ms Jones and well-built.
Lawyers said Mr Williams had family in the Swansea area.
Mr Justice Roderic Wood said the youngsters were "vulnerable".
He said last week another High Court judge, Mr Justice Hedley, had decided that Ms Jones had "abducted" the children from Spain, where they were in the care of their father.
Ms Jones had been ordered to return the children to Spain by midnight on Friday 12 October but had not done so.
Late on Friday she had been ordered to attend a High Court hearing in London on Monday.
"The mother came to my court yesterday and argued through her barrister that the order of Mr Justice Hedley ... should be set aside," said Mr Justice Roderic Wood.
"I declined to set that order aside."
He added: "I was also concerned that the mother might abscond overnight and so I, with a heavy heart, ordered that the children were to be immediately removed from the mother's care and placed in the care of the local authority for a short period of time so that they could be returned to Spain without delay.
"When they police came to remove the children very early this morning from the mother's house in Llanelli, Wales they found the mother and the children had gone."
The judge said Ms Jones had "abducted" the children before.
"This is the second time this mother has abducted the children from Spain," he said. "The last time she did so was in 2009."