The EU urged Italy on Thursday to allow more time to discuss its threat to suddenly stop vessels from other countries disembarking migrants in Italian ports, after rescuing them in the Mediterranean.

Brussels said it was ready to give Italy fresh financial support to deal with the crisis but said Rome had to give due warning of such a drastic step.

Italy issued the threat on Wednesday as the number of arrivals swelled, with more than 10,000 people rescued from rickety boats off Libya since Sunday alone.

We support and we understand Italy's concern and we support their call for a change in the situation, European Commission spokeswoman Natasha Bertaud told reporters.

But what we're also saying is that any change in policy should first be discussed with other member states, and also properly communicated to the NGOs who are running these boats so that they have time to prepare.

EU migration commissioner Dimitris Avramopoulos had met Italy's representative to the European Union, Maurizio Massari, to discuss the issue, she added.

Several aid ships chartered by privately-funded organizations from France or Germany are taking part in efforts to rescue migrants from the Mediterranean.

Most of them disembark the migrants in Italy, and under EU rules the country where a migrant lands is responsible for dealing with their claim for asylum.

One of the charities operating rescue boats, SOS Mediterranee, said on Thursday that it understood the pressure Italy was under and the need for more coordinated European action.

Libyan coast guards carry a baby off a boat during the rescue of 147 illegal immigrants attempting to reach Europe off the coastal town of Zawiyah, west of the capital Tripoli, on June 27, 2017. (Photo by AFP)

However, we also believe that closing the ports of safety to people seeking refuge from war, violence and poverty cannot be the solution, the aid group said in a statement.

We would like to stress again that NGOs are not the cause, nor the solution to this humanitarian crisis. Without our presence at sea, even more people would die.

Speaking after talks with other European leaders in Berlin, Italy's Prime Minister Paolo Gentiloni said Rome was extremely concerned about the recent surge in migrant boat arrivals, but appeared to play down the threat of closing ports.

We are confronted with growing numbers that over time could severely test our reception system, Gentiloni said. We have internationalized search and rescue operations but reception remains for only one country.

This is putting our country under pressure but we will respect our humanitarian and legal commitments. We are under pressure and we are asking our European partners for a concrete contribution.

Nearly 77,000 migrants have landed in Italy since January, up 15 percent on the same period in 2016. An Italian source told AFP: We can't go on like this.

Bertaud said the EU was ready to increase support to Italy including additional substantial financial assistance when the bloc's interior ministers meet next week.

But the row plays into deeper divisions in the EU over sharing the burden of the migration crisis that has gripped the continent since 2015.

Countries such as Greece and Italy want more support, but some eastern European nations are refusing to take their share of migrants from frontline states under a controversial relocation scheme agreed by the EU two years ago.