Sri Lanka vowed Thursday to keep up a controversial anti-narcotics drive after a UN complaint that some of the more than 40,000 people arrested had been tortured in police custody.

Last week the UN's human rights chief Volker Turk, said Operation Yuktiya -- the Sinhala word for "justice" -- had been responsible for a series of police abuses since it began last month.

Public Security Minister Tiran Alles told a press conference in Colombo that he was unconvinced by the allegations and said the crackdown was in the best interests of the island nation.

"The Human Rights Commission has a duty to tell us 'okay, these are the incidents and get our answers," he said.

"They can issue statements, but I will not stop this operation," he added. "We know that we are doing something good for the children of this country, for the women of this country."

The UN said security forces had reportedly conducted arbitrary arrests, public strip searches and torture of suspects in custody.

Alles said only around a tenth of the more than 40,000 arrested in the anti-drugs campaign had been detained while others had been bailed to face criminal possession charges.

He claimed that the operation had seen a considerable decline in the amount of narcotics available on the streets since December.

Local rights activists have accused police of arresting drug users and small-time dealers without pursuing bigger players in the trade.