Rome: Dozens of migrants were feared dead on Thursday after a migrant boat overturned some 30 miles off the Libyan coast while at least 88 were rescued by Italian coastguard, its commander Cosimo Nicastro said. Two Italian coastguard vessels raced to the scene of the shipwreck after the boat was spotted by an aircraft participating in the European Union's Mediterranean monitoring operation, Nicastro said. It not known how many migrants were travelling aboard the boat. Libyan coastguard also reported finding four bodies as well as also two empty boats during two operations on Thursday that rescued 766 migrants off the coastal cities of Sabratha and Zwara. The Italian navy rescued 562 migrants from a capsized people-smuggling ship on Wednesday. The navy initially said seven bodies had been recovered in that operation but then lowered the number to five. Dramatic images of Wednesday's shipwreck showed migrants clinging to the ship's sides and being thrown into the sea, many without life-jackets on. Some 6,000 migrants trying to reach Europe have been rescued from flimsy craft in the Mediterranean this week alone. It is feared there could be many more victims as people-smugglers in lawless Libya take advantage of warm weather and calmer seas to pack passengers into unseaworthy boats for the perilous crossing. Aid agencies say the crossing between Libya and Italy is the main route for migrants since a recent European Union deal with Turkey curbed the number sailing across the Aegean to Greece.