Rome - Italy's decision to keep hundreds of would-be immigrants in an overcrowded reception centre on a tiny island poses a security and sanitary risk, a spokeswoman for the United Nations' refugee agency warned Wednesday.

Laura Boldrini, of the United Nations High Commissioner for Refugees, said the "unsustainable conditions" were due to recent Italian government provisions seeking the immediate repatriation of immigrants entering the country illegally by sea.

Some 1,800 people - including over 200 who landed on Tuesday - are staying at the centre on Lampedusa - a facility which can accomodate a maximum of 800.

Boldrini said the current situation at the otherwise "model" facility, threatens the safety of the immigrants and its staff, including aid workers and medical personnel.

Interior Minister Roberto Maroni on a visit to the island earlier this month said the migrants would no longer be relocated for identification to centres elsewhere in Italy, but would instead be expelled immediately.

The government's decision amounts to "the suspension of the guarantees" for asylum seekers under Italian law, Boldrini said.

In terms of the law, immigrants who apply for political asylum must be accomodated in centres where, unlike on Lampedusa, they are allowed freedom of movement.

But Maroni, who is from the anti-immigration Northern League party in Prime Minister Silvio Berlusconi's coalition, says the asylum-seeking procedures are often used by those not eligible for refugee status as a means to avoid repatriation.

The interior minister, in his visit to Lampedusa, promised there will be no repeat this year of the situation experienced in 2008 when 31,000 migrants landed on the island.

Maroni also said a recent bilateral agreement with Libya will allow the Italian navy to patrol the North African nation's coastline, an area from where many would-be immigrants attempt to cross the Mediterranean and reach Italy.

A total of 36,900 would-be immigrants arrived in Italy by sea in 2008, a 75 per cent increase over the previous year. (dpa)