"Fundamentally, this is a breach of the principle of no forced returns. That's a clear violation of international law," said Adrian Edwards, spokesman for the UN high commissioner for refugees (UNHCR).
Sri Lanka has deported 88 Pakistanis since August 1, despite claims that they could be at risk in their homeland, Edwards said.
Starting with men who had been placed in detention, the country has widened the net to cover whole families, he told reporters.
"We are very concerned at the continued deportations that are happening.
We want deportations stopped."
In all, there are now 11 women and eight children among the deported, said Edwards.
"Some of the latest deportees had their passports and asylum-seeker certificates seized last week.
They were told to go to Colombo airport, where they were placed on flights to Pakistan," he said.
He added that UNHCR staff had also heard of families being separated -- including a man sent home over a week ago and whose pregnant wife remains