Libyan authorities arrested 400 illegal migrants, including several pregnant women, at dawn on Sunday as they prepared to board boats for Europe, officials said. Most of the migrants were Somalis and Ethiopians and included "pregnant women", said Mohammed Abdelsalam al-Kuwiri, spokesman for a unit in the Tripoli-based government that combats illegal migration.
He said they were arrested as they were getting ready to board boats in Tajura, east of the capital.
An AFP photographer said dozens of migrants were taken by car to a detention centre in Tripoli.
A migration squad official said the arrests coincided with the launch of an operation targeting people smugglers.
The operation, run by the Tripoli-based government which is not recognised by the international community, calls for "co-ordination between various security services", the official said.
The government in Tripoli was created by the powerful Fajr Libya militia alliance last August during a power struggle with the internationally recognised administration now based in the east.
Fajr Libya is one of several heavily armed militias that have been vying for power in Libya since the end of the 2011 uprising that toppled veteran dictator Muammar Qadhafi.
Jihadists from the Islamic State group have also gained a foothold in the oil-rich North African country, feeding on the political breakdown and lawlessness.