The aid group Doctors Without Borders said Tuesday attempts by various European Union nations to deter migrants have put thousands of people in danger and created more business for smugglers.
In a report, it said border closures and tougher policing only encourage people seeking sanctuary or jobs to use other routes to get to Europe.
The group's head of operations, Brice de le Vingne, said "policies of deterrence, along with their chaotic response to the humanitarian needs of those who flee, actively worsened the conditions of thousands of vulnerable men, women and children."
The group urged the EU to create more legal ways to come to Europe and allow asylum applications at the land border between Turkey and Greece.
- Refugee girls, women subject to sexual violence en route to Europe, says rights group
- Bodies of at least 36 migrants, including children, found on coast of Turkey
- Germany says nearly 1.1 million people registered as asylum-seekers in 2015
More than 1 million migrants arrived in the EU last year, but they have not always been welcomed.
Dutch police said Tuesday they arrested three protesters the previous night at a demonstration against a town's plan to build a centre for asylum-seekers.
Riot police cleared a central square in the town of Heesch after demonstrators began throwing eggs and fireworks at officers. Police say there were no injuries.
The demonstrators were protesting plans, not yet been formally approved, to build a centre for 500 asylum-seekers in Heesch, a village of some 13,000 inhabitants 100 kilometres southeast of Amsterdam. Last week, someone hung a pig's carcass from a tree near the proposed location.
Meanwhile, the European Union's top migration official says so-called "hotspots" should be up and running in Greece and Italy within a month in an effort to better control how migrants flow into the bloc and conduct early security checks on them.
The hotspots intended to register new arrivals, take fingerprints and other data, and perform background checks. Those with no chance of asylum would quickly be sent home, while others would be more evenly distributed among EU nations.
Migration Commissioner Dimitris Avramopoulos was quoted by Germany's Sueddeutsche Zeitung on Tuesday as saying he sees no immediate end to the flood of asylum seekers and that it's critical to get hotspots running quickly.