Demonstrators forced many Chicago businesses to keep their employees home Monday.  Protests at the NATO summit in the city's downtown area led to increased security and revised train and bus routes designed to dodge the summit zone, the Chicago Tribune said.

Many businesses told their employees to stay home during the second and final day of the summit because of heavy traffic and the possibility of more protests.

Metra rail stations along a line that carry roughly 14,000 riders in from southern suburbs were closed and stations and platforms were being patrolled by law enforcement and K-9 units.  The Chicago Transit Authority also rerouted 24 buses through the summit zone.

On Monday, demonstrators from the Occupy Chicago movement planned to protest outside Boeing Corp.'s headquarters.  The protests were expected to be smaller than the weekend's events, the Tribune said.

Sunday saw the biggest conflict as protesters clashed with police for several hours at the end of a march through downtown, the New York Times said.  About 45 protesters were arrested, and at least four officers were injured, according to Chicago Police superintendent Garry McCarthy.

The march was led by about 40 men and women in American military uniforms who said they wished to return their medals as symbolic gestures.  Thousands of protesters opposed to war and to NATO or motivated by other issues then marched down Michigan Avenue, headed toward McCormick Place, where world leaders discussed the war in Afghanistan, European missile defense and other security issues at the summit.

At least two men received charges for having explosives while three others were arrested for considering an attack against President Barack Obama's re-election campaign headquarters, the house of Mayor Rahm Emanuel, police stations and financial institutions.