A child has died after a boat carrying migrants capsized off the Greek island of Lesbos, in what is believed to be the first reported death since Turkey announced it was opening its borders with Europe last week.

The makeshift boat was carrying 48 people, accompanied by the Turkish coastguard when it entered Greek waters early Monday, Greece's coastguard said in a statement.

The passengers “overturned the boat” as it was approached by the coast guard, according to Greek officials, who added this was a “common tactic” used by traffickers to force a rescue.

Of the passengers, 46 were “recovered unharmed” and two unconscious children were taken to hospital in Lesbos, the coast guard said. One of these children later died.

The death comes days after the Turkish government announced it would no longer stop refugees from attempting to cross by land or sea into Greece, saying it had “reached its capacity.”

The announcement prompted migrants to head north to the Greek border, leading to clashes with Greek border guards. Greece has not opened its side of the border and has beefed up its presence along it.

The move tramples on a 2016 deal struck with the European Union to halt migrants travelling from the Middle East towards Europe. Ankara said Europe had failed to hold up its end of that pact.

The developments come on the back of an airstrike by Russian-backed Syrian forces that killed 33 Turkish soldiers in Idlib, Syria last week. Turkey's about-face on its migrant deal with the EU is seen as a way of leveraging European support for its military operation in Syria.

CNN's Niamh Kennedy and Chris Liakos contributed to this report