An audio recording in which migrant children in the US can be heard crying for their parents has been released as US President Donald Trump remains defiant over his immigration policy.
Some 2,000 migrant children have been separated from their parents in the past few months after their families tried to cross the US border illegally.
Mr Trump said he would not allow the US to become a “migrant camp”.
The UN high commissioner for refugees says the policy is “unacceptable”.
The recording was released by investigative US media outlet ProPublica on Monday, and was said to have been made from inside a US customs and border protection facility.
In it, several Central American children separated from their parents and thought to be aged between four and 10 can be heard sobbing and wailing, and calling for their mother or father.
One border patrol agent can be heard saying: “We have an orchestra here. What’s missing is a conductor.”
The UN High Commissioner for Refugees, Filippo Grandi, has told the BBC the Trump administration’s “zero-tolerance” policy towards illegal immigration is unacceptable.
“It is absolutely wrong to separate children from their families in any circumstances and particularly when people are in distress as, for example, people that are fleeing from violence and persecution, as is the case for people in Central America,” he said.
“So, we are advising the government of the United States that this is not the right way to handle that particular phenomenon of people seeking asylum across the border.”
On Monday, Mr Trump said the US would “not be a migrant camp”, or a refugee-holding facility.
“You look at what’s happening in Europe, you look at what’s happening in other places.
“We cannot allow that to happen to the United States. Not on my watch.”
The Republican president blamed Democrats for not coming to the table to negotiate immigration legislation.
Meanwhile, Mr Trump’s job approval rating averaged 45%, according to Gallup polling conducted last week. This matches his previous peak, in the first week after his inauguration in January 2016.