The body of a child believed to have drowned in a migrant boat accident washed up on a beach on the Greek island of Lesbos Sunday, the Greek coastguard said.

The body of the girl, between four and six years old, was found "in an advanced state of decomposition and without a head", the statement added.

Local media reports and coastguard sources had earlier said it was believed the body was that of a girl missing after a boat sank off the east of Lesbos last month.

The body, found by locals on Lesbos's Vatera beach, is at the hospital for an autopsy.

Hours later, according to the Greek coastguard statement, the body of a woman also in an advanced state of decomposition was discovered washed up at another beach. Because of its condition, it was initially reported that the body was that of a man.

On Thursday, two children were among three people who died when a migrant boat sank near the Greek island of Samos.

More than 200 refugees and migrants have died so far this year trying to cross the Mediterranean, most headed towards Italy, according to the International Organisation for Migration.