The United Nations refugee agency has criticised the way Italy has handled boatloads of migrants arriving on the southern island of Lampedusa.
Boatloads of illegal immigrants continue to head for Lampedusa
UNHCR envoy Juergen Humburg says Italy has flown many of them back to Libya, without considering if any are in genuine need of political asylum.
Italian Prime Minister Silvio Berlusconi is due to visit Libya on Thursday to discuss the crisis.
Italy says the expulsion flights will continue in the short term.
"The process of expelling illegal immigrants who arrive by sea will be completed over the coming days as the situation evolves," the interior ministry said in a statement.
Rai Radio 1 said the flights stopped on Tuesday as Libya struggled to deal with the numbers of people being sent back.
Italy has sent at least 11 planeloads of migrants to Libya since Friday, in a dramatic change of policy introduced after more than 600 people arrived on Lampedusa in one night.
More than 1,000 migrants, all claiming political asylum, have arrived from North Africa in the past few days. The island is the nearest geographical point of arrival in the European Union from North Africa.
Mr Humburg, sent to investigate the situation, left the island on Tuesday after he was denied entry to the detention centre where 500 of the latest arrivals were being held.
He said the Italian government had to find ways to identify the asylum-seekers and the refugees among them.
"It is not acceptable from our point of view to reject these people just because they arrive in big numbers," he said.
"If we find ways to have orderly departure programmes, for example, of a higher resettlement quote which would allow refugees and asylum-seekers to reach European countries in conditions of safety, I think it would be better for all.
"Even if we have mass influxes of people who are fleeing persecution and human rights violations, we cannot make it a question of numbers. They should be given access to a safe country, to asylum, to protection."
The Italian government has defended the policy, saying the repatriations will discourage people from setting off.
Mr Berlusconi's trip to Libya will be his second in less than two months. He is expected to discuss with Libyan leader Colonel Muammar Gaddafi ways of stemming the numbers of illegal immigrants heading for Italy.
A group of 21 illegal immigrants, mostly Eritreans, were rescued from their sinking canoe as they headed for Lampedusa overnight, according to French news agency AFP.
They were taken to a holding centre on the island.