Geneva: An outside expert working with the UN human rights office has corrected a figure he cited claiming that over 100,000 children were currently being held in migrant detention in the United States.

Manfred Nowak, who leads a UN Global Study on Children Deprived of Liberty that was published this week, told reporters: "We have more than - still more than - 100,000 children in migration-related detention in the United States of America." Reuters, Associated Press, ours and other major news organisations reported that figure.

Migrant children taken into custody at the US-Mexico border await their fate in a Texas migrant camp in June. Credit:AP

But later he told AP that figure was drawn from a UN refugee agency report citing data from 2015, the latest figure his team could find. That was before US President Donald Trump, whose policies on migration have drawn criticism, was elected. The president at the time was Barack Obama.

Nowak, a professor of international law at the University of Vienna, also said the figure of more than 100,000 referred to the cumulative number of migrant children held in detention at any point during that year, whether "for two days or eight months or the whole year," not all simultaneously.