MYTILENE (Greece) • Tens of thousands of migrants massed on Greek islands yesterday as the president of the European Union warned that the refugee crisis would last for years and the United Nations pleaded for a worldwide solution.

With Greece's migration minister Yiannis Mouzalas admitting the island of Lesbos was "on the verge of explosion", the authorities opened a new centre to process the 30,000 refugees stuck there and on other Aegean Sea flashpoints, with Athens promising more for other bottlenecks.

Greece's migrant reception agency said it had asked the EU for emergency medical aid, bedding equipment and over €9.5 million (S$15.1 million) to support reception services on Lesbos, Samos and Kos and to send an operational unit to Chios.

Lesbos mayor Spyros Galinos said procedural pressures were easing after an additional 140 personnel arrived from Athens to handle migrant and refugee registration. "Some 7,000 people were registered yesterday and we expect at least the same number today," he said.

Hours earlier, a handful of coast guards and riot police armed with batons had struggled to control some 2,500 migrants in Lesbos' main port, screaming, "keep back", as the crowds surged towards a government-chartered ferry bound for Athens.

EU president Donald Tusk warned that the "human haemorrhage" to Europe would be long-lasting.

"The wave of migration is not a one-time incident, but the beginning of a real exodus, which means that we will have to deal with this problem for many years to come," Mr Tusk said in a speech at the Bruegel Institute, a think-tank in Brussels.

In Geneva, the UN's special representative for migration and development, Mr Peter Sutherland, said countries worldwide must be asked to do their share.

AGENCE FRANCE-PRESSE