Dozens of migrants were rounded up in the Libyan capital Tripoli on Monday in the country's latest crackdown.
And neighbouring Tunisia said on Monday that more than 650 migrants were intercepted or rescued trying to reach Europe by sea at the weekend.
In Libya, police said security forces detained many migrants in raids on dwellings in Tripoli’s Airport Road area early on Monday.
Dozens of migrants were pictured sitting on the ground in an open area surrounded by armed forces.
The raids followed an increase in crimes including prostitution, robbery and drug trafficking in the area, police said. The statement said legal measures would be taken against the migrants.
Reports said the migrants were likely to be taken to detention centres in Tripoli — places that rights activists say are rife with abuse and where migrants are kept in miserable conditions.
A spokesman for the Tripoli-based government did not answer calls seeking comment.
Two migrants killed while collecting refuse
Over the weekend, a vehicle hit two migrants working as refuse collectors in the Airport Road area. Both were killed.
Last year, security forces detained more than 5,000 migrants, including many women and children, in a section of Tripoli in what authorities described as a security campaign against illegal migration and drug trafficking.
The UN decried the clampdown, which involved harassing migrants at their homes, beatings and shootings.
Sea crossing attempts tend to increase during spring and summer.
In Tunisia, 657 people were rescued or prevented from trying to cross in 46 separate incidents between Friday and Monday, maritime and military officials said on Monday.
The Italian island of Lampedusa is just 140 kilometres from Tunisia's east coast.
The coast guard thwarted 10 attempted crossings overnight, bringing ashore 156 would-be migrants, the National Guard said.
Two thirds of them were from sub-Saharan Africa and the rest were Tunisians.
The previous night, the National Guard said it had foiled 11 other attempts, preventing 219 people from migrating, including 113 from sub-Saharan African countries.
Meanwhile, defence ministry spokesman Mohamed Zekri told AFP that 42 Egyptians who had set sail from neighbouring Libya were rescued on Sunday off Kerkennah, central Tunisia, after their boat sank and they took refuge on an oil platform.
Tunisia is in the throes of political and economic crises, while Libya has been gripped by lawlessness since 2011 and militias have turned to people trafficking.
The two countries are also the gateway for sub-Saharan Africans hoping for a better life by escaping impoverished and strife-torn countries such as Sudan.