At least 21 asylum seekers have died and 30 more are missing after two boats sank in separate incidents off the coast of Greece within 24 hours.

At least 16 women migrants, one man, and one boy died when their vessel sank off the Greek island of Lesbos early on Thursday, in the second disaster involving refugees in the Aegean Sea in under a day, the country's coastguard said.

The sunken boat was carrying about 40 people, with 17 bodies recovered, a coast guard official said. Ten women were rescued and around a dozen people were presumed missing.

READ MORE

Will Russia's referendum raise nuclear threat?

Iran promises 'transparent' Amini investigation

Chinese student comes to soprano's rescue

The boat sank east of Lesbos, one of the Greek islands closest to the coast of Turkey, an important route for asylum seekers trying to reach the European Union.

Greek Migration Minister Notis Mitarachi in tweet demanded Ankara take "immediate action to prevent all irregular departures due to harsh weather conditions.

"Already today many lives lost in the Aegean, people are drowning in unseaworthy vessels. EU must act," he wrote.

Two tragedies in 24 hours

In the earlier incident on Wednesday, Greek emergency services managed to bring 80 asylum seekers - among them 18 minors - on to land after their boat sank after hitting a rocky area in stormy waters near the island of Kythira in southern Greece.

According to those rescued, 15 were still missing and a search operation was being carried out along the wider coast of Lesbos for those who may have made it to shore. Three were found trapped in a remote area.

"Strong winds blowing in the area are making our work difficult," coast guard spokesperson Nikos Kokkalas said.

Greece was at the front line of the 2015 migration crisis, when around a million refugees fleeing war and poverty in Syria, Iraq and Afghanistan arrived in the country, mainly traveling through Turkey.

The number of arrivals has declined since then. However, Greek authorities say they have recently experienced an increase in attempted entries through the country's islands and land border with Turkey.

Blame game

On Thursday, Shipping Minister Plakiotakis accused Ankara of not preventing human traffickers from exploiting asylum seekers and demanded it respect a 2016 deal with the European Union to stop them from trying to enter Europe in the first place.

"As long as the Turkish coast guard does not prevent their actions, traffickers will pile unfortunate people, without safety measures, into boats that cannot withstand the weather conditions," he said.

Turkey says it has increased measures in recent years to prevent people smuggling, while repeatedly accusing Greece of pushing back migrants and sinking their boats, something that Athens denies.

However, last month a delegation of Green European MPs accused Athens of creating what they called a "wall of lies" to conceal the pushback of asylum seekers back over its borders with the approval of Frontex, the EU agency responsible for policing asylum seekers along the bloc's borders.

New Democracy, Greece's ruling conservative party "is trying to build a different reality" and raising a "wall of lies," according to German MEP Erik Marquardt, speaking at a news conference ahead of a meeting with the Greek migration minister.

Last June, Athens denied statements made in a UN report saying that its border surveillance forces had illegally sent thousands of migrants back over its borders within the past two years.

But Dutch Greens MEP Tineke Strik in late September said that pushbacks are "happening on a systematic scale."

"We have numerous reports from credible sources," she said.