Masked Shiite militiamen armed with rocket launchers and automatic weapons poured through the streets of this southern Iraqi city on Tuesday, setting up roadblocks to protest U.S. military action in Najaf. About 200 militiamen supporting Shiite cleric Muqtada al-Sadr blocked roads in Basra with burning tires and broken concrete blocks. They could be seen in groups of about a dozen at main intersections in the city. Witnesses said most shops were shut and government offices were closed down as a result, but Squadron Leader Spike Wilson, a British military spokesman, said the roadblocks had little affect. "Iraqi police service (is) pretty much in control of the center of Basra," he told The Associated Press. "There's certainly not widespread activity and the barricades are only there temporarily. When the police and (Iraqi National Guard) move into the vicinity, they seem to disappear."