Some 2,000 migrants brandishing placards with 'freedom' written on them protested against tougher new asylum rules on Greek island of Lesbos.
Clashes erupted after police blocked protesters who were marching towards the port capital of Mytilene and police have to fire tear gas to disperse demonstrators.
Greek government is trying to speed up the process of repatriating the migrants whose asylum requests have been rejected.
A migrant holds a child during clashes with riot police on Monday. AFP
Boris Cheshirkov, Greece spokesperson for the UN refugee agency said in a statement that a significant backlog of pending applications and serious delays in asylum procedures have been a major contributing factor to the dangerously overcrowded conditions on the islands.
"Long waiting times are also contributing to the mental toll that people are facing," he said.
Migrants react during clashes with riot police on the island of Lesbos on Monday. AFP
At present Greece faces a backlog of almost 90,000 asylum applications, according to a UN estimate.
Greece has become the first port of entry for migrants and refugees entering Europe last year.
A young migrant reacts during clashes with riot police on Monday. AFP
Greece has struggled to manage the influx of migrants which has resulted in overcrowding of camps on the Aegean Greek islands near the Turkish coast.
Aid agencies have condemned the living conditions at camps on five islands where over 40,000 asylum-seekers are currently kept.
Refugees and migrants confront riot police during clashes. Reuters
At Moria, where over 19,000 people live in and outside a camp built for fewer than 3,000, many are housed in tents and makeshift shelters without access to power, heating, or hot water.
The new Greek minister for migration Notis Mitarachi has vowed to expel "on a weekly basis" migrants whose asylum applications are rejected.
Agence France-Presse