Police in Chicago have arrested at least 45 protesters after clashes with authorities outside the NATO summit.

Thousands of anti-war protesters took part in the largely peaceful demonstrations Sunday. But late in the afternoon, some of the protesters tried to push through a line of police keeping them from the lakeside convention center where leaders and delegates from 50 countries are meeting.

Police in riot gear used batons to respond to the demonstrators after several protesters threw bottles and other objects at the officers. Police officials said four officers suffered minor injuries in the clashes.

The protest Sunday followed several smaller demonstrations over the previous two days, which were also mostly peaceful.

Earlier Sunday, police said two men were in custody on charges of planning to make bombs for use during the NATO meetings.

Those arrests followed terrorism charges against three other men Saturday for possession of explosive devices. Police say in that case, the men plotted to use the devices in an attack on President Barack Obama's campaign headquarters in Chicago, the home of the city's mayor, Rahm Emanuel, and other targets.