Clashes on the Greek island of Lesbos

Clashes erupted between police and refugees on the Greek island of Lesbos on Tuesday, with authorities describing Lesbos as "on the verge of explosion".

Around 2,500 refugees surged towards a government-charted ferry bound for Athens. As the crowds desecended upon the main port, tens of coastgaurds and riot police screamed "keep back" and tried to control the situation. 

The scenes of chaos underscored the difficulty authorities across Europe face as they struggle with a surge of people making a hazardous trek through the continent as they flee war and misery in their home countries.

Many protested the waiting conditions, while others tried to jostle their way to the front.

Lesbos is home to 85,000 people, and according to the United Nations refugee agency, is now hosting more than 20,000 mostly Syrian refugees arriving on its shore.

"It seems that over the weekend the numbers (of arrivals in Greece) surged and then died down," Melissa Fleming, spokeswoman for the UN refugee agency said, pointing out that there were "30,000 refugees on the Greek islands right now."

With other Greek islands close to Turkey also overwhelmed, the European Union president Donald Tusk insisted "the wave of migration is not a one-time incident but the beginning of a real exodus, which only means that we will have to deal with this problem for many years to come."