Italy denied on Wednesday that it supported a deal to pay armed groups implicated in human trafficking to prevent migrants crossing the Mediterranean.
The Associated Press reported on Tuesday that Libya's U.N.-backed government in Tripoli, as part of a deal backed by Italy, was paying militias and giving them equipment and boats to prevent migrant vessels setting off.
"The foreign ministry firmly denies that there is an agreement between Libyan traffickers and the Italian government," an official from the Italian ministry's press office said.
"The Italian government does not deal with traffickers", the official added.
A new force in the Libyan coastal town of Sabratha is preventing people leaving, often by locking them up, sources in the area have told Reuters, prompting a sudden drop in departures at what is usually the busiest time of year for migration.
Arrivals from North Africa dropped by more than 50 percent in July and more than 80 percent so far in August. Some 600,000 have made it to southern Italy by sea since 2014.
In a bid to manage migrant arrivals ahead of a national election due by May next year, Italy has taken action including providing training and equipment to Libya's coastguard, and laying down rules for non-governmental sea rescue organisations.
Progress in Libya is likely to be fragile, as two governments are vying for power, and local militias are battling over territory and smuggling profits.