MOSCOW—Police arrested nearly 1,500 people Wednesday during a day of demonstrations throughout Russia calling for freedom for imprisoned opposition leader Alexei Navalny, whose health reportedly is in severe decline after three weeks of hunger striking, according to a group that monitors political detentions. The largest of the protests took place in Moscow, where thousands marched…

MOSCOW—Police arrested nearly 1,500 people Wednesday during a day of demonstrations throughout Russia calling for freedom for imprisoned opposition leader Alexei Navalny, whose health reportedly is in severe decline after three weeks of hunger striking, according to a group that monitors political detentions. The largest of the protests took place in Moscow, where thousands marched…