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U.S. warns of threat against Americans in Italy

ROME, Italy (CNN) -- U.S. citizens could be the targets of terrorist attacks in four Italian cities this weekend, the U.S. Embassy in Rome warned Wednesday.

In an announcement, the embassy said credible information indicated extremist groups may be aiming for Americans in Venice, Florence, Milan and Verona on Sunday, the Christian Easter holiday.

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"The U.S. government continues to receive credible reports that extremists are planning additional terrorist actions against U.S. interests," the statement said. "These groups do not distinguish between official and civilian targets."

Civilian targets, the embassy said, may include facilities where Americans are known to congregate or visit such as clubs, restaurants, places of worship, schools or outdoor recreation events.

The announcement urges Americans to increase their security awareness and to avoid large crowds.

In Washington, a State Department official said that the United States has received information indicating Americans could be targeted on Easter.

"The credibility of these threats is undetermined, but it was city and date specific," said the source, who added that authorities did not know if the threats were connected to Osama bin Laden's al Qaeda network.

On the Easter weekend, "generally you have huge gatherings in Rome and [across] Italy," the official said.

As of now, the source said, State Department facilities in Italy will remain open.

Wednesday's announcement is the second such advisory about U.S. citizens in Italy since September 11. A State Department worldwide caution for all Americans remains in effect.

CNN Rome Bureau Chief Alessio Vinci and Producer Elise Labott contributed to this report.