WASHINGTON, Jan 31 (Reuters) - Amid a fresh outbreak of political violence in Kenya, the United States on Thursday alerted Americans to the risk of traveling to the troubled East African nation.

Political and ethnic violence has killed 850 people in Kenya since the disputed Dec. 27 re-election of President Mwai Kibaki. The killing of an opposition legislator on Thursday sparked new protests and fatal clashes.

The State Department said the situation in Kenya was volatile and subject to change on short notice, adding that some U.S. officials had been temporarily moved from the western port city of Kisumu to the capital, Nairobi.

"A recent outbreak of protests in Nairobi and violent civil unrest in Kisumu, Nakuru, and Naivasha demonstrates the potential for spontaneous violence in the current political climate," the State Department said in a travel alert.

The alert urged U.S. citizens to avoid travel to those cities and other areas outside Nairobi. It also warned American travelers to be prepared for a sudden outbreak of clashes between police and demonstrators or rival groups of demonstrators.

"Even demonstrations intended to be peaceful can become violent," the alert warned. "Americans should therefore avoid all demonstrations, protests and large public gatherings."

(Writing by JoAnne Allen; Editing by Eric Beech)

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