Coastguard spokesman General Ayoub Qassem said 431 people on four inflatable boats were rounded up between Thursday and Saturday at sea off the town of Sabratha, 70km west of the capital, Tripoli.
“The illegal migrants are from various sub-Saharan countries and include a big number of women and children,” said Qassem.
“Smugglers had tried to foil the process of arrest by opening fire on our coastguards but the coastguards fired back and that forced the smugglers to withdraw,” he added.
According to Qassem, 700 migrants had been picked up on January 27 from three wooden vessels in the same area.
Among them were refugees from Syria, Tunisia, Libya and the Palestinian Territories.
Libya has become the main point of departure for people attempting to cross the Mediterrenean Sea by boat to various parts of Europe, ever since a route between Turkey and Greece was largely closed off in 2016.
People smugglers based in Libya have operated with impunity, sending migrants across the sea in vessels that occasionally break down or sink before they can be saved by rescue boats.
Libya’s coastguard sends migrants back to detention centres that rights groups have criticised for inhumane conditions and widespread abuses.
At a meeting in Malta, EU leaders agreed on a strategy to help curb the number of refugees departing from Libya in upcoming months.
Under the new plan, the bloc would provide Libya’s government with funds to increase efforts to stop migrant boats from crossing territorial waters, and to “break the business model” of traffickers who helped 181,000 migrants enter the EU through Libya and Italy last year.
The announcement received a backlash from human rights groups who said such plans exposed migrants to further risks and abuses.
An estimated 230 people have died en route to Europe since the start of 2017, according to the United Nations.
More than 4,500 people died attempting the crossing last year.