The U.S. Embassy in Addis Ababa has issued a heightened security alert a day after Ethiopia's government warned of an imminent terrorist attack.  VOA's Peter Heinlein in the Ethiopian capital reports the alert coincides with a government roundup of ethnic Oromos, including several prominent citizens, on suspicion of collaborating with terrorists.

An e-mail sent by the U.S. Embassy in Ethiopia advises Americans in the country to avoid public gatherings and public places.  The message specifically mentions hotels as places to avoid.

The message was sent less than 24 hours after Ethiopia's Anti-Terrorism Task Force warned of an imminent terrorist attack and urged citizens to be vigilant.

Police recently rounded up about two dozen members of Ethiopia's largest ethnic community, the Oromos, and charged them with aiding terrorists.  Among those arrested were the top managers of two of Addis Ababa's finest hotels, as well as the leader of one of the largest Oromo political parties.

Witnesses say those detained were told during a courtroom proceeding that they were suspected of collecting money and sending it to known members of the Oromo Liberation Front, an armed insurgent group.

Bereket Simon, senior adviser to Prime Minister Meles Zenawi was quoted earlier as saying the leader of the Oromo Federal Democratic Movement, Bakele Jirata, had been working 'hand in glove' with terrorists.

In an e-mail sent to VOA this week, the OLF said its fighters had killed 31 Ethiopian soldiers in a clash October 31 in eastern Oromia region.  The message told of two other similar clashes earlier in the month.  Government spokesman Zemedkun Tekle dismissed the OLF message, calling it fabricated, and an attempt by the rebels to get attention.

Police were out in force in Addis Ababa after the security alert.

Security was especially tight around the city's best hotels, but diplomats and political observers cautioned not to read too much into the timing of the terrorist warning and the arrest of prominent Oromos. 

They note other violent insurgent groups also operate in Ethiopia, including the Ogaden National Liberation Front, which is blamed for several suicide bombings last week in the Somaliland and Puntland regions of neighboring Somalia. 

The ONLF is also blamed for a deadly attack on a Chinese-run oil exploration site in Ethiopia's Ogaden region last year.

The leader of Ethiopia's largest Oromo party, Merara Gudina, tells VOA he does not understand why the crackdown is occurring.

"Really I could not make heads nor tails of it except that the government is sometimes routinely harassing Oromos and political activists, [and] all of us on the legal platform especially during the elections.  These things are routine," he said.

Merera, who heads the Oromo National Congress, and the leader of the Oromo Federal Democratic Movement parliamentary bloc both vehemently deny any involvement with the OLF insurgency. 

Oromos are Ethiopia's largest ethnic community, making up as much as 35 to 40 percent of the country's estimated 80 million people

Ethiopia's capital has been the scene of several terrorist attacks this year.  In May, a bomb blew up in a taxi van in front of the Hilton Hotel, killing six people, including a man with dual U.S. and Israeli citizenship.  A coordinated series of gas station bombings killed three people in April, and a blast in a public hall last month killed four and injured more than 20 others.