Europe's abandoned border posts

European governments have got themselves into a tangle as more than a million migrants and refugees have floated in on Greek waters since the start of 2015, then trekked chaotically northwards towards wealthier EU states, mainly Germany and Sweden.

The official EU response to the biggest migration wave since the aftermath of World War Two - championed by German Chancellor Angela Merkel since last August - is for member states to pull together and share the burden of providing shelter for people, especially Syrians, fleeing war or persecution, while securing the bloc’s external borders.

But in reality, most members have failed to take their agreed quotas of refugees and nearly a dozen countries have built barriers to try to keep both migrants and refugees out.

The bloc is now trying to implement a deal which would see Turkey take back all new arrivals, in return for Europe resettling a limited number of Syrians directly from Turkey.

Some 170,000 migrants have arrived in Europe by sea so far this year, according to the International Organization for Migration, mostly through Greece and fleeing the war in Syria.

The European Commission set out a timetable in early March to restore the fraying Schengen area by year-end.

It proposed no new measures, but told European Union countries to abide by existing EU law and stop the "wave through" approach that has led to migrants and refugees marching north through the Balkans from Turkey through Greece.

The Schengen Agreement, with the goal to eliminate internal border controls, was signed more than 30 years ago.

Open internal borders are widely seen as a major achievement of European integration that have facilitated travel, tourism, trade and supply chains across the bloc, fuelling economic growth.