The Italian coastguard is working to rescue 1,200 people aboard two boats at sea which have got into trouble.
One of the boats carrying 400 people was previously reported to be taking on water with those on board in “imminent danger of death”.
The fishing boat had been located by a plane operated by German NGO Sea-Watch International.
It had set off from Tobruk in Libya but has been adrift at sea.
The other rescue operation by the Italian coastguard on Monday was to help a fishing boat carrying 800 people that was located over 120 miles southeast of Siracusa, in Sicily.
It said in a statement this operation was complicated by the number of people on board.
A spokesperson for coastguard said it would take hours to complete the two ongoing operations because of difficult conditions, including the long distance form the coast.
Before these two operations, the Italian coastguard had already rescued around 2,000 migrants since Friday, it said.
The Mediterranean Sea is one of the world’s busiest migration routes and has claimed thousands of lives.
Read more from Sky News:
British woman falls from hotel balcony
Two dead after Marseille explosion
China and Taiwan in tense naval stand-off
Be the first to get Breaking News
Install the Sky News app for free
There has been a surge in numbers trying to cross the Mediterranean from North Africa over the Easter weekend.
Another NGO, Germany’s Resqship, said on Sunday it helped a wreck on Saturday and found about 25 people in the water, who said they had been there for two hours.
“Our crew was able to recover 22 survivors and two deceased,” the aid group tweeted, adding that survivors said about 20 people drowned.
The group’s ship, the Nadir, took the rescued migrants to the Italian island of Lampedusa.
“We are angry. This is an unspeakable tragedy that could – and should – have been prevented by a humanitarian approach to migration instead of barb-wiring the European borders,” ResQship said.
Last week, 440 migrants were rescued off Malta after a complex 11-hour operation in stormy seas by the Geo Barents
vessel of the Doctors Without Borders (MSF) charity.
So far this year some 35,976 people have arrived in European countries such as Italy, Greece and Spain via the sea, according to the United Nations High Commissioner for Refugees.
At least 443 people are believed to have died seeking to enter Europe in the region.
