Several dozen migrants being detained at a holding camp on the Greek island of Lesbos protested behind the barbed wire fence of the compound on Tuesday, shouting ‘We want freedom!’

They were among thousands of refugees and migrants who have arrived on Lesbos on or since March 20 from Turkey and who are being held under a new EU agreement with Ankara until their asylum requests are processed and they are accepted or sent back.

The first group of 202 migrants, most from Pakistan, were returned to Turkey on Monday from Lesbos and the Aegean island of Chios.

Through barbed wire at the Moria camp on Lesbos, one man held up a piece of cardboard, which read: ‘Kill us if you want.’

On the wall of the sprawling gated complex, which was once an army camp, graffiti read: 'No one is illegal'.

The European Union and Turkey reached a deal in March to seal off a route used in the past year by hundreds of thousands of migrants, many fleeing conflict zones.

In return, the EU will take in thousands of Syrian refugees directly from Turkey and reward it with financial aid, visa-free travel and progress in its EU membership negotiations.

Reporters have been barred from entering the Moria site, initially set up to register arrivals.

The United Nations refugee agency UNHCR stopped transporting arrivals to and from the site since it became what it calls a ‘detention centre’.

Other aid groups have pulled out from the site in protest at conditions there.

UNHCR says there are some 600 people above capacity at Moria, including pregnant women, lactating mothers and children, with insufficient food.

Just over 172,000 refugees and migrants have arrived by sea in Europe through the first weekend in April, the International Organization for Migration (IOM) said on Tuesday.

The figure includes small numbers of migrants arriving in Cyprus and Spain, as well as the busier routes connecting Turkey to Greece and North Africa to Italy, the agency said in a statement.