ATHENS - A boat carrying an unknown number of refugees and migrants sank off Greece's Lesbos island early on Monday and five bodies have been recovered on a shore north of the island, the Athens News Agency reported.The Greek coast guard was not immediately available for comment.Growing numbers of migrants are attempting the crossing in flimsy, overcrowded boats as the spring weather improves. Nearly 9,000, mostly Africans, were rescued over the long Easter weekend, UN aid agencies said."Europe needs to rescue people because it cannot allow them to die at its own back door," said Chris Catrambone, an American businessman who co-founded the Migrant Offshore Aid Station (MOAS), with his Italian wife Regina in 2014.He was speaking by telephone from the MOAS rescue vessel Phoenix, which after a frantic weekend's activity was heading slowly towards Sicily with 463 migrants on board, including 170 women and children, and seven dead bodies recovered from the sea.The crossing from Libya to Italy is now the main migrant route into Europe. More than 181,000 came to shore in Italy last year, and arrivals this year are up about a third on the same period of 2016.Some 850 are estimated to have died so far in 2017. That is fueling a dispute over whether laying on more rescue vessels, and patrolling closer to Libya, is encouraging the flow of migrants and boosting the profits of people-smugglers.Since Italy abandoned its search-and-rescue mission in 2014, the European Union's border control agency Frontex has taken over patrolling the Mediterranean, but its ships remain well clear of the Libyan coast.