Italy's coastguard rescued about 170 migrants on two separate rubber boats in Mediterranean waters, news agency AGI reported Friday, hours after a crisis hotline signalled they were in distress.  

Some 79 migrants were rescued first and brought to the Italian island of Lampedusa, followed by another 90 people, it said.

Alarm Phone, a non-profit organisation that provides a rescue hotline for migrants at sea, had signalled late Thursday the presence of a "precarious" rubber dinghy "in distress" in an area within Malta's search and rescue area. 

On Friday morning, the volunteer group said on Twitter they were still in contact with the boat, as well as with another dinghy that had previously contacted it. 

"We're relieved about some good news amidst all the bad!" tweeted Alarm Phone on Friday, saying that a third boat carrying about 70 people had also arrived in Italy.

The coast guard did not respond to calls seeking more information.  

Warm weather over the past week has encouraged more migrants fleeing war and poverty to make the perilous trip across the Mediterranean, but about 100 people drowned on Thursday alone. 

The UN's International Organization for Migration (IOM) reported a shipwreck off Libya on Thursday that killed at least 74 migrants, including children. 

Hours later, Doctors Without Borders said another 20 people died after another boat overturned. 

On Tuesday, humanitarian ship Open Arms said at least five migrants died after an overcrowded rubber dinghy overturned off the coast of Libya.