The European Union must introduce a new, automatic system of taking in migrants saved from the Mediterranean, the leaders of Italy and France said on Wednesday, as they sought to patch up bruised bilateral relations.

Italy has long complained that it has been left alone to deal with the hundreds of thousands of migrants who have crossed the sea in recent years looking for a better life in Europe.

The issue has caused particular tensions between Rome and Paris, with Italy complaining that French non-governmental organizations have been instrumental in rescuing migrants but that France has not done enough to help take them in.

But French President Emmanuel Macron has leaped on the fact that a new, pro-European government has taken office in Italy to try to reset ties and resolve the long-standing row.

"I do not underestimate what Italy has been experiencing since 2015. It has also suffered many misunderstandings and injustices," Macron told reporters in Rome, standing alongside Italian Prime Minister Giuseppe Conte, at the press conference.

"I am convinced that an automatic European mechanism is needed for the reception of immigrants," he added.

Conte said he had received French backing for a system to handle the redistribution of migrants, meaning that Italy could rely on the entire 28-nation bloc to accept automatically a share of all the new arrivals as soon as they were rescued.

Macron, speaking through an interpreter, said EU countries that refused to take part in the scheme should be "seriously penalized". They did not provide further details, saying only that the issue would soon be discussed by EU interior ministers.

"The issue of immigration must no longer fuel anti-European propaganda," Conte said, referring to his previous coalition partner, the far-right League, which has seen its popularity surge thanks to its anti-migrant agenda.