Italy has called on the European Union and UN to set up operations in African countries to help stem the flow of migrants heading for Europe.

"We have to go to the root (of the problem) and discourage these men and women from leaving their countries," Prime Minister Matteo Renzi told deputies in a statement to parliament on his objectives for Thursday's emergency EU summit on the Mediterranean migrant crisis.

"There has to be a strong presence of the international organisations in the area south of Libya. It is vital that the EU as a bloc tries to go into these areas along with the United Nations."

Renzi specifically mentioned Libya's neighbours Niger and Sudan, both transit countries for migrants making their way to Libya, where people traffickers are able to operate with impunity because of the absence of any central authority in the conflict-torn country.

The Italian premier did not go into the detail of what UN agencies should do in the African states.

A number of European countries have raised the idea of asylum seekers having their requests for refuge in the EU assessed before they get to the point of embarking on life-risking crossings of the Mediterranean.

Officials have also raised the idea of a pilot scheme to provide funds for migrants deemed to have no claim to enter the EU to be fast-tracked back to their countries of origin.

Carrying out triage operations of this kind in Libya is not feasible at the moment because of the security situation in the country, which has resulted in many Western governments withdrawing nearly all of their diplomats.

Renzi said he was hopeful that EU governments would belatedly hear Italy's pleas for help in coping with the challenging migrant flow following a weekend disaster in which 800 people are feared to have perished in a shipwreck off Libya.