A boat engine has exploded at sea near Libya, killing at least 45 people, including five children, according to the United Nations.The United Nations said in a statement that the incident took place near the Libyan port of Zawara on Monday, with 37 people rescued by fishermen, most of them from African countries, all in custody.According to the United Nations, this is the worst accident at sea so far this year.Illegal immigrants usually use the Libyan coast to reach Europe via Italy and Malta.