About 3,000 people have been saved in the Mediterranean Sea in a single day while trying to make the journey from northern Africa to Europe, according to the Italian coastguard.

They were picked up in more than 20 separate rescue operations on Saturday, involving the Italian coastguard and navy, the EU's EUNAVFOR mission in the Mediterranean, European Union border agency Frontex, NGOs, and merchant ships.

The coastguard gave no details of the nationalities of those rescued.

According to the International Organisation for Migration (IOM), so far this year 43,490 refugees and migrants have arrived in Europe by sea as of April 26.

More than 1,000 have died or are missing.

Earlier this month, Angelino Alfano, Italian foreign minister, said his country will host an international conference on migration.

"The stabilisation of Libya has a tremendous value for us [Italy]: it means national security, the end of human trafficking, and a reduction of the migration flow," Alfano was cited as saying in the Italian Ansa news agency.

Refugees and migrants who pass through conflict-ridden Libya endure harsh conditions.

The refugees and migrants - many from Nigeria, Senegal and The Gambia - are captured as they head north towards Libya's Mediterranean coast, where some hope to try and catch boats for Italy.

Along the way, they are prey to an array of armed groups and people-smuggling networks that often try to extort money in exchange for allowing them to continue.

READ MORE: What is the world doing for migrants?

Last month, the IOM said many refugees and migrants have been held for ransom, kidnapped, made to perform forced labour and, in some cases, sold in markets as slaves.

Some of those who cannot pay their captors are reportedly killed or left to starve to death, the IOM said. When migrants die or are released, others are purchased to replace them.

Libya is the main gateway for people attempting to reach Europe by sea, with more than 150,000 people making the crossing in each of the past three years.