More than 6,900 migrants have been rescued from the central Mediterranean, in one of the largest ever single-day operations, the International Organization for Migration (IOM) said Tuesday.

The Italian coastguard coordinated 35 interventions on Monday, intercepting 44 dinghies, eight small wooden boats, one ship with 200 on board and another carrying 704 people, Flavio Di Giacomo, an IOM spokesman in Rome, told dpa.

‘Nearly 7,000 people in a day is really quite a lot. If it's not a record, then it's close to it,’ he said.

Di Giacomo said two bodies were recovered, but the cause of death was not yet known. They were due to be taken in the southern port of Brindisi on Wednesday, along with 720 survivors, the local mayor said, as quoted by the ANSA news agency.

Rescue operations were continuing Tuesday, the IOM spokesman added.

The Italian navy and coastguard, British, Irish and Norwegian vessels, as well as a ship run by the Doctors Without Borders (MSF) charity, were involved in Monday's operations, IOM said in a statement.

MSF ship Dignity I picked up ‘twins who were premature babies delivered at eight months and were 5 days old,’ medical team leader Antonia Zemp said in a separate statement from her organization.

They were moved along with their mother to a boat that could take them onshore to Italy because ‘one of the boys was not well. He was vomiting, had hypothermia and was non-reactive,’ Zemp said.

Prior to Monday's rescue, August had been a relatively quiet month for sea migrant arrivals, with about 12,600 compared to 23,500 during August 2015, IOM data showed. ‘Abnormally windy’ sea conditions may have kept some boats from leaving North Africa, Di Giacomo said.

Since border controls were tightened earlier this year along the so-called Balkan route, connecting Turkey to Austria, Italy has replaced Greece as the main entry point for Europe-bound migrants from Africa, the Middle East and beyond.

The IOM calculated that 163,000 people arrived in Greece since the start of the year, compared with 234,000 in the same period of 2015. In Italy, there were 111,500 arrivals in the year to date, compared to 116,000 from January to August of last year.