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GENEVA Aug 2 (Reuters) - The bodies of 120 migrants believed to have been trying to reach Italy by boat from Libya have been found off the Libyan coast over the past 10 days, the International Organization for Migration (IOM) said on Tuesday.

"We are getting this information from Libyan authorities that we are collaborating with," said IOM spokesman Joel Millman. The bodies had been discovered near Sabratha and had not come from previously known shipwrecks in the Mediterranean.

Mainly African migrants are taking often unseaworthy boats from Libya to Italy, gateway to Europe. Nearly 8,000 were rescued at sea between Friday to Monday on that central Mediterranean route, Millman told a briefing.

It is a longer and more perilous journey than that from Turkey to Greece, largely shut down since a deal was struck between the European Union and Turkey in March, although 174 migrants did make it by sea to Greece over the weekend, IOM said.

More than 257,000 migrants and refugees have already entered Europe by sea this year through July 27, and for the third straight year, at least 3,000 others have died, the agency said.

A total of 4,027 migrants or refugees have perished worldwide so far this year, three-quarters of them in the Mediterranean, Millman said.

The figures represents a 35 percent increase on the global toll during the first seven months of 2015, he said. (Reporting by Stephanie Nebehay; Editing by Richard Balmforth)