A least 14 migrants have died after their their boat sank in the Mediterranean between Libya and Italy, the Italian news agency ANSA reported, citing rescuers.
ANSA said Italian coast guard and navy vessels were taking part in the rescue near an offshore oil platform.
A coastguard earlier told the AFP news agency that at least 200 people had been rescued and Italian media said around 400 people had been on board.
The coastguard said the rescue was being carried out by two commercial ships that were scrambled to the area, some 185km south of Lampedusa island, Italy's southernmost point.
A Libyan navy spokesman, Colonel Ayub Kassem, said Libya "does not have the means to help with this shipwreck, which took place in international waters".
Kassem said he could not confirm that the migrant boat had departed from Libya.
The latest incident comes days after after another migrant boat sank off the Libyan coast, killing 36 migrants.
In the past week alone, more than 4,000 migrants have reached Italy's shores, arriving in smugglers' boats. Many of the boats set out from Libya's loosely patrolled coast with migrants that are fleeing wars or hardship in Syria, Eritrea and elsewhere.
More than 400 migrants drowned in twin tragedies off Lampedusa last year.
Immigration charities estimate that up to 20,000 migrants have died at sea trying to reach Europe over the past 20 years.