General Ayoub Qassem said 205 Africans including eight women and a child were rescued early on Monday off the coast of Tajura, 30km east of Tripoli,
The migrants “were on two inflatable dinghies that had started to take on water”, he said.
On Sunday, the coastguard rescued 215 migrants including 47 women off Zwara, 160km west of Tripoli, Qassem said.
“They are thought to have jumped or fallen off the boat during the night,” the spokesman said.
“The smugglers pushed two dinghies crammed with people out to sea before removing their engines and abandoning them to their fate.”
Qassem did not say where the boats departed, but most leave from western Libya, just 300km from the Italian coast.
The Italian coastguard said it had also rescued another 3 000 migrants off the coast of Libya on Sunday.
The North African country has long been a stepping stone for migrants dreaming of a better life in Europe, but people smugglers have stepped up their lucrative trade in the chaos since the 2011 ouster of longtime dictator Muammar Gaddafi.
Interior ministers mainly from the central Mediterranean region met in Rome Monday to ramp up efforts to curb migration from Libya.
They released a declaration of intent which limited itself to promising increased coordination and information sharing in a bid to tackle the root causes of migration, as well as combat smuggling and strengthen borders.