Those saved on Sunday had left Libya aboard eight overloaded inflatable dinghies and two fishing vessels, they said.
They were picked up by Italian coastguard and naval vessels, a British and an Irish warship and several ships chartered by humanitarian NGOs.
The Aquarius, hired by the groups SOS Mediterranee and Doctors without Borders (MSF), said it had picked up 252 people, including women and small children.
On Saturday, 2,300 people were rescued from 18 small boats, heading to Italy.
The weekend's arrivals come on the heels of a big migrant wave at the end of August, when more than 14,000 people were plucked to safety in the space of five days. Most were from sub-Saharan Africa.
According to Italy's interior ministry, about 124,500 migrants have arrived since the start of 2016, just slightly more than the 122,000 recorded for the whole of last year.
Italy is sheltering growing numbers of would-be refugees as its neighbours to the north move to tighten their borders and make it harder for migrants to travel to their preferred destinations in northern Europe.
According to interior ministry figures this month, Italy now has 155,000 migrants in reception centres, compared with 103,000 in 2015 and 66,000 in 2014.