By Brad Brooks, Phil Stewart, Idrees Ali and Dietrich Knauth LOS ANGELES (Reuters) -Hundreds of U.S. Marines arrived in the Los Angeles area on Tuesday under orders from President Donald Trump, as the city's mayor declared a curfew for parts of the downtown area and police arrested 197 people in a fifth day of street protests.

A cloud of uncertainty is hanging over Los Angeles, where questions remain over the role that Marines and National Guard troops will play after being called in by President Donald Trump amid protests over immigration raids in the city.

A curfew for downtown Los Angeles is now in effect. It began at 8 p.m. local time and will last until 6 a.m. The curfew applies to an area about one square mile in downtown LA, which has been the site of clashes between police and protesters over the past several days.