BRUSSELS - European leaders argued into the early hours on Friday over how to handle over a migrant crisis in the Mediterranean, agreeing a plan to share out the care of desperate people fleeing war and poverty in North Africa and the Middle East.

Determined not to be dragged into negotiations over Greece's debt debacle at their summit in Brussels, leaders instead found themselves sparring for seven hours about whether to take in 40,000 Syrian and Eritrean asylum seekers now in Italy and Greece and another 20,000 people currently outside the EU.

They eventually agreed a voluntary scheme, sticking to the 60,000 number but granted an exclusion for Hungary, which earlier described the plan as absurd, as well as for Bulgaria, one of the EU's poorest countries.

"It was a very intensive debate," German Chancellor Angela Merkel told reporters after the meeting ended, describing the migrant crisis "as the biggest challenge I have seen in European affairs in my time as chancellor".

Expressing his frustration, Commission President Jean-Claude Juncker described the plan as one of "modest ambition".

"We have to find out if the system works. It doesn't matter if it is voluntary or mandatory, it is whether it can help 60,000 refugees," Juncker told a news conference in the early hours of Friday.

However, the EU's chief executive had been hoping to set a precedent for Europe-wide action that limited national opt-outs.