European Council President Donald Tusk expressed alarm over the build-up of migrants in Libya, and warned that Italy and Malta would be quickly overrun if they start moving towards Europe.

"We must remember that the Balkan route is not the only one and that other countries also expect our cooperation and solidarity, not only Greece and Bulgaria. I have in mind here the Central Mediterranean route. The numbers of would-be migrants in Libya are alarming. This means that we must be prepared to help and show solidarity to Malta and Italy, should they request it," Tusk said.

The European Union has seen more than a million migrant arrivals in the last year, with most of them entering via Greece. Now, worries are arising over possible new illegal migrant routes. Nearly 10-thousand people arrived in Italy by sea last month, compared with less than 2,300 people in March 2015. The total number of migrants to Italy this year hit just below 20-thousand.

Meanwhile, more than 150-thousand people have already arrived in Europe via Greece this year, though arrivals from Turkey have slowed, due to an agreement with the EU.