Italy failed to respect international standards in deporting 25 African migrants who arrived on a ship operated by a German relief group, the U.N. refugee agency said Friday.

In a letter to Italian authorities, the U.N. High Commissioner for Refugees "expressed its strong concern over apparent disregard for accepted international and European standards and for fundamental elements of due process," agency spokesman Rupert Colville said.

Italy put the 25 asylum seekers on a plane to Ghana on Thursday, drawing protests from humanitarian agencies and opposition politicians. Five refugees were flown Tuesday night to Nigeria. The others, some who were taken off Thursday's plane for causing a disturbance, also will be expelled, Italian officials said.

The deportees were among 37 Africans permitted to dock in Sicily on July 12, after the German vessel they were on had plied the Mediterranean for weeks in search of a friendly port.

The ship's operator - relief agency Cap Anamur, based in Cologne, Germany - said it rescued the Africans at sea on June 20 and that some said they were refugees from Sudan's Darfur region, which the United Nations says is suffering the world's worst humanitarian crisis.

Italian officials said this week that the refugees were from Nigeria and Ghana.

One Nigerian was granted permission to stay in return for cooperating with authorities investigating the ship's voyage, the Interior Ministry said.

UNHCR had previously applauded the Italian government's decision to allow the 37 migrants to dock for humanitarian reasons, but said it "regretted serious flaws in the subsequent handling of the asylum seekers."

Shortly after the group disembarked, it appears diplomats from several countries - including Sudan - were brought to see the migrants despite their declared intention to seek asylum, UNHCR said.

Exposing possible refugees to a representative of the government that may be responsible for their flight is "contrary to basic refugee protection principles," UNHCR declared.

The U.N. agency also said that Italy's Central Commission, responsible for determining refugee status, appears to have been under pressure to deny the asylum claims, with authorities informing the media that none of the Africans was a refugee even before the commission had started interviews.

The asylum seekers also were not given proper access to legal council, Colville said, and UNHCR had limited access to the group.