At least 217 migrants have been intercepted on their way to Italy and taken to the overcrowded holding centre on the island of Lampedusa.
An official said the migrants had been spotted in a single, ill-equipped boat off the tiny island west of Sicily, amid worsening sea conditions.
The boat came from Libya, the official said, though it was not clear where the passengers had originally come from.
There was only one woman on board, and no children, the official said.
The migrants' boat was about 15m (49 feet) long, the official told the Associated Press news agency.
It was intercepted by the Italian authorities before dawn.
The immigrants were taken to a centre on Lampedusa, which was only built to hold 190 people but was already catering for 203, Italian newspaper La Repubblica said.
One report said the new arrivals came from a number of different African countries, while according to another, they said they were from Iraq and the Palestinian territories.
The route from Libya to Italy's Mediterranean islands is a common one for people hoping to reach Europe from Africa and the Middle East.