ROME – American citizens could be targeted by extremist groups in four Italian cities on Easter Sunday, the U.S. government warned Wednesday.
The State Department said a "possible threat exists to U.S. citizens in the cities of Venice, Florence, Milan and Verona on Easter Sunday from extremist groups."
The announcement did not identify the groups or elaborate on the nature of the threats, but it warned that "these groups do not distinguish between official and civilian targets."
It said Americans should "increase their security awareness and avoid large crowds."
A U.S. official said the warning was based on information developed in cooperation with Italian authorities.
In Washington, Secretary of State Colin Powell said, "For those who are traveling in Italy — in specific places that were mentioned — be prudent, be careful; enjoy yourselves but display some caution in your activities, where you are, travel together."
State Department spokesman Richard Boucher refused to give details about the threats or say who was behind them.
"Frankly, the American that may be under a threat or may encounter the threat doesn't really care who it is that's attacking. So it's not an essential piece of information for us to put out," he said.
Italian anti-terrorism officials refused to comment on the threats, but the Interior Ministry and police officials in all four cities said security would be stepped up for Easter.
The ministry said security would be tightened in airports, train stations and ports. Cities famed for their art treasures which attract large numbers of tourists would get special attention, it said.
Defense Minister Antonio Martino said the potential targets should be avoided: "I'll try to stay home."
Another U.S. official, speaking on the condition of anonymity, described the threats as uncorroborated and unspecific, but from a credible source. The official said the threat came from Islamic extremists. It's unclear whether they have ties to Al Qaeda.
Earlier this month, the United States warned that extremists were planning terrorist actions against American interests. That warning was issued after the March 17 attack on worshippers at a Christian church near the U.S. Embassy in Islamabad, Pakistan. Two Americans and three other people died in the attack.