NEW YORK (AFP) - At least 70 immigrant children separated from their parents on the southern US border were transferred to shelters in New York as the state prepares to sue the government over the practice, Governor Andrew Cuomo said.

"We know of at least 70 children who are being held in federal facilities across New York State. That number is expected to increase," Cuomo said Tuesday (June 19) on Twitter.

NY1 local television crews filmed a small group of Spanish-speaking young girls, most likely separated from their accompanying adults at the border, at East Harlem's Cayuga Centers shelter in the early morning hours Wednesday (June 20).

The images further stoked fury against family separation in the Democratic majority state, with critics asking why New York agreed to take in the children instead of fighting for reunification.

New York's population of unaccompanied children is more than 1,300 - 311 of whom were separated from their parents at the border - the New York Daily News reported, citing a federal source.

Cuomo announced that New York state will in less than two weeks file a multi-agency lawsuit against President Donald Trump's administration "for violating the constitutional rights of immigrant children and their families who have been separated at the border."

He branded the separation of families as "a moral failing and a human tragedy." New York Mayor Bill de Blasio also spoke out against children being transferred to New York.

"I want to see anything we can do to stop NYC from being used as a place to send children separated from their parents," he told local media on Tuesday.

Children separated at the border are transferred by the Office of Refugee Resettlement to the northeastern state, where they have so far been placed in at least 10 shelters. Other children have been transferred to different shelters across the country, Cuomo added.

The ORR is responsible for placing unaccompanied children in accommodation until relatives or family friends can be found to act as guardians. In cases where that is not possible, the children enter foster homes.

Generally, unaccompanied children are placed in shelters in states where they have relatives who later take them into their homes.

"But these are not unaccompanied alien children. These are children who were separated from their parents," Cuomo told local media.

More than 2,432 undocumented children were separated from their parents at the US-Mexico border between May 5 and June 9.

US doctors have warned that the trauma caused by these separations can be long-lasting, triggering mental illness, behavioural problems and developmental setbacks.

Colleen Kraft, president of the American Academy of Pediatrics, has called the separations "a form of child abuse".