More than 4,000 migrants rescued in single day

ROME -- More than 4,000 would-be refugees were rescued at sea Thursday in one of the busiest days of the Mediterranean migrant crisis, and at least 20 died trying to reach Europe as Libyan-based smugglers took advantage of calmer seas to send desperate migrants north.

The death toll was likely to grow far higher, however, as the Libyan coast guard also reported two overturned boats between the coastal cities of Sabratha and Zwara. Only four bodies were found, raising fears the rest of those on board had perished.

But, a Libyan Navy spokesman said a total of 766 migrants were rescued by the Libyan coast guard Thursday.

Col. Ayoub Gassim said they were found in two groups: one of 550 near the western coastal city of Sabratha and the second of 216 off Zwara.

Overall, the Italian coast guard said it had coordinated 22 separate rescue operations Thursday that saved more than 4,000 lives.

"That probably is a record," said coast guard spokesman Cmdr. Cosimo Nicastro, noting previous highs have been in the range of 5,000 to 6,000 over two days.

Before this week's deaths, the International Organization for Migration said only 13 people had drowned in the month of May, compared with 95 last May and 330 in May 2014. It said the figures "indicate that migrant fatalities may at last be declining" thanks to beefed-up coast guard monitoring along the North African coast.

However, improved weather conditions appear to have led to an increase in the number of migrants risking the crossing.