At least 11 people have died and more than 60 are missing as a result of two shipwrecks off the coast of southern Italy, rescuers say.

German charity RESQSHIP said it picked up 51 people from a sinking, wooden boat and found 10 bodies trapped in the lower deck near the island of Lampedusa on Monday.

In a separate incident on the same day, more than 60 people were reported missing, with 26 of them feared to be children, Médecins Sans Frontières (MSF) said.

The boats were carrying migrants who had set off from Libya and Turkey, UN agencies said.

Survivors of the shipwreck near Lampedusa were handed over to the Italian coastguard and taken ashore on Monday morning, while the deceased were being towed to the island, according to RESQSHIP.

The boat had set off from Libya, and was carrying migrants from Syria, Egypt, Pakistan and Bangladesh, the UN refugee agency UNHCR, the International Organization for Migration (IOM) and UN children's agency UNICEF said in a joint statement.

The other shipwreck was located about 125 miles off the coast of Calabria in southern Italy, the agencies said.

One of the surviving 12 people died after disembarking, the Italian coastguard said.

MSF's Shakilla Mohammadi said she heard from survivors that 66 people were unaccounted for, including at least 26 children, some only a few months old.

"Entire families from Afghanistan are presumed dead. They left from Turkey eight days ago and had taken in water for three or four days. They told us they had no life vests and some vessels did not stop to help them," she said in a statement.

The Mediterranean is the deadliest known migration route in the world.

More than 23,500 migrants have died or gone missing in its waters since 2014, according to UN data.