Greece has started to send migrants back to Turkey this morning as part of an EU agreement to control the mass influx of people in Europe.

Two boats left the Greek island of Lesbos at around 5.30am carrying 131 people.

Under the deal, Ankara will take back migrants and refugees, including Syrians, who entered Greece illegally.

In return the EU will reward Turkey with more money, early visa-travel and progress in its EU membership negotiations.

One of the boats leaves Lesbos. Credit: APTN

Around 750 migrants, mostly from Pakistan and Afghanistan, are expected to be returned today.

But there are concerns there will not be enough staff to handle it as border management agency Frontex has reportedly only recruited a tenth of the 2,300 officers it needs to do the job.

Each migrant must be accompanied by one official who will escort them to make sure they get on the boats.

Around 500 migrants are expected to be returned to Turkey. Credit: Reuters

The agency relies on the EU's 28 member states to provide translators and other officials to process asylum seekers.

However, these have not been forthcoming, even as the continent faces its worst refugee crisis since the Second World War.

There are reportedly not enough staff to handle the situation. Credit: Reuters

What is the EU migrant deal?

Under the agreement, migrants arriving illegally in Greece will be returned to Turkey if they do not apply for asylum or if they make an asylum claim that is rejected.

For every person sent back, EU countries will take in one Syrian refugee confirmed to have made a legitimate asylum request.

The deal was originally supposed to take effect immediately, on March 19, but has faced delays due to the shortage of personnel and other problems.

Thousands of migrants are still camped at the Greece-Macedonia border. Credit: Reuters

On Sunday another 514 migrants arrived in Greece bringing the total number in the Aegean islands to more than 6,000.

Giorgos Kyritsis, a spokesman for the Greek government's refugee crisis committee, said: "We do not know how this operation will proceed.

"This is being done for the first time and it raises unprecedented legal issues as well."

The Greek government must also deal with more than 46,000 migrants and refugees now on the mainland.

More than 20,000 live in makeshift camps on the northern border with Macedonia and in Athens.