LESBOS, Greece (Reuters) - More aid agencies helping refugees and migrants arriving in Greece said they were joining a boycott of detention centers on Wednesday, angered at an EU deal they say runs roughshod over human rights.

Refugees and migrants wait to be transferred to the Moria registration centre after arriving at the port of Mytilene on the Greek island of Lesbos, following a rescue operation by the Greek Coast Guard at open sea, March 22, 2016. REUTERS/Alkis Konstantinidis

Human rights organizations reject the pact between the European Union and Turkey to fast-track registration and asylum applications, under which hundreds of new arrivals have been detained since Sunday. Refugees or migrants whose applications fail will be sent back to Turkey.

Aid agencies said cooperating with the Greeks at detention centers would make them complicit with an “unfair and inhumane” practice.

Two aid agencies said on Wednesday they were following the U.N. refugee agency UNHCR and aid organization Medicins Sans Frontieres (MSF), a major contributor to the relief effort, which both announced on Tuesday they would cut back assistance.

“The IRC alerted the (Greek) coast guard on Monday that we would not transport the world’s most vulnerable people to a place where their freedom of movement is impeded upon,” said Lucy Carrigan, a regional spokeswoman for the International Rescue Committee (IRC).

The IRC will continue to support those at another makeshift camp, she said.

The Norwegian Refugee Council, a major non-governmental organization, said it was suspending most of its activities at a detention center on the Greek island of Chios.

Slideshow ( 2 images )

“We are extremely close to be in a position where this site is dangerously overcrowded ... We have a large number of refugees including pregnant women and children lying on the concrete floor in the reception hall,” said Dan Tyler, a protection adviser for the council.

Tension in the facility was building up and there had already been demonstrations, he told Reuters.

THOUSANDS STRANDED

Thousands of people have been stranded in Greece since a cascade of border shutdowns in the Balkans started in February.

There are almost 50,000 refugees and migrants stranded in Greece, the vast majority of them not detained in camps since most arrived before the new EU arrangement came into effect on March 20.

Some 12,000 are at Idomeni, a sprawling complex of tents on the Greek border with Macedonia. Since Tuesday, MSF medical personnel have been absent from the camp, citing security reasons after two migrants tried to set themselves on fire.

Migrants living at Idomeni blocked a motorway and a customs checkpoint on Wednesday, demanding that the border be opened.

Greek authorities said they needed help. “We need these international organizations, particularly the UNHCR, which is of great assistance to us. Naturally we want it to stay, under certain rules, of course,” Citizen Protection Minister Nikos Toskas told Greek radio.

A government source said migration minister Yannis Mouzalas was trying to coax aid organizations back.

“He is the best placed to mediate with these groups,” the source said. Mouzalas, a physician, was extensively involved with aid agencies and participated in relief missions before his cabinet appointment in Greece’s leftist-led government last year.

More than 147,000 people, many fleeing conflict in the Middle East and Asia, have arrived in Greece by sea this year. Almost one million arrived in Europe via Greece in 2015.