Four migrants died when their boat capsized off the Greek island of Lesbos, while 18 people were rescued, the coastguard said.

A patrol picked up 22 people in the Aegean but four of them were dead, a brief statement said.

The survivors were transferred to Mytilene, the main city on Lesbos, along the main passage route for migrants coming in from Turkey.

No details were given about the nationalities or the condition of those rescued.

In June, an overcrowded fishing trawler carrying up to 750 people who had been picked up in Libya sank off Greece.

Around 100 of them were saved, but it is thought that some 600 drowned, according to Greek figures.

Thousands of migrants, mostly from Syria, Afghanistan and Pakistan, have entered Greece in recent years from the sea and land borders with Turkey.

Following a strict migration policy, Greece has stepped up patrols in the Aegean Sea between Greece and Turkey with the help of the European Border Surveillance Agency, Frontex.