Trouble is increasing in Burundi, where on Dec. 4 rebels warned foreigners to leave the country and fired on a passenger plane landing at the international airport in Bujumbura, the capital. Two people were injured aboard the plane. A curfew is in effect in the city from midnight to 5 a.m., and the U.S. Government prohibits its personnel from flying in and out of the city after dark because of the heightened risk of violence at the airport at that time. Rebel groups are active in the Great Lakes region, and travel to the area should be avoided.