CALAIS, FRANCE/BUDAPEST: Hundreds of migrants poured overnight onto the high-speed railway linking Paris with London near the French port of Calais, stranding thousands of passengers in darkness for hours aboard Eurostar trains.

At the EU's opposite end, another angry crowd camped outside a Budapest train station demanding to board trains for Germany, as Europe's asylum system crumbled under the continent's biggest migration crisis since the 1990s Balkan wars.

Hundreds of thousands of refugees fleeing wars and economic migrants escaping poverty have arrived in the European Union in an unprecedented wave that has confounded EU leaders and fed the rise of right wing populists.

Nearly all first reach the EU's eastern and southern edges and then press on illegally for richer and more generous EU countries further north and west.

The EU's executive European Commission promised to unveil a new policy next week to make it easier to process asylum claims, distinguish bona fide refugees from other migrants, send those from safe countries home and distribute those with genuine asylum claims among the bloc's 28 members.

Meanwhile, authorities have struggled to enforce rules which ordinarily allow free movement within the EU but not to undocumented migrants.

Hundreds took to the tracks around France's Calais-Frethun station, the latest target for those trying to reach Britain, which many regard as a better place to live than countries on the continent.

Rail operator SNCF was forced to halt services near the entrance to the Channel Tunnel. Three Eurostar trains were blocked overnight and eventually continued to London early on Wednesday, while two returned to their departure stations.

Passengers on one London-bound train, which stopped less than a mile (1.6 km) from the tunnel, were told at one point to keep quiet and listen for people on the roof. A helicopter with a searchlight circled as guards walked the tracks.

With the power out, passengers sat in stifling darkness for nearly four hours. A woman in business class wept.

Eurostar later pulled the train back to Calais, where passengers disembarked for fresh air and bottled water.

About 3,000 to 4,000 migrants from the Middle East, Asia and Africa camp near Calais, dodging police as they try to board trains and trucks heading to Britain through the tunnel or on ferries. They have disrupted passenger and freight transport between Britain and France throughout the summer.

A spokeswoman for Eurotunnel (GETP.PA), which operates the railway tunnel beneath the channel, said that as security has been tightened at Calais port and the tunnel entrance, migrants have sought new entry points such as Calais-Frethun, about 5 km (three miles) inland, beyond a zone controlled by Eurotunnel.