CHICAGO: Anti-war protesters staged a peaceful march on the headquarters of US defense contractor Boeing in Chicago on Monday after several days of demonstrations during a meeting of Nato leaders.

Between 200 and 300 demonstrators, some throwing paper planes, gathered in a festive atmosphere that contrasted with fierce clashes with police that led to dozens of arrests and a number of injuries on Sunday.

Occupy Chicago, the local chapter of the loose-knit anti-Wall Street Occupy movement, had promised to shut down Boeing Co's headquarters, which it called “Nato's war machine,” and demanded the alliance stop military operations around the world.

“There's absolutely nothing that could happen in the streets at a protest that holds a candle to the death and destruction caused by Nato to families and communities all around the world,” said Rachel Perrotta of Occupy Chicago.

The demonstrators gathered only briefly outside Boeing's building and then moved on.

A Boeing spokesman said most of the 500 employees had been urged to stay home and work remotely. Metal barricades protected ground-level windows at the headquarters building, which was guarded by police and security guards.

“We want people to be safe. The office is open today though we've encouraged people to work remotely from home,” said Boeing spokesman John Dern.

Police said they arrested 45 protesters on Sunday, most of them in a melee at the conclusion of a largely peaceful march by 3,000 protesters to the edge of a security zone around the Nato summit site. Four police officers had minor injuries.

A lawyers' group defending the protesters said more than 60 were arrested and two dozen injured by police using batons on protesters who had been ordered to leave.

One protester sustained a head wound requiring 10 stitches, another suffered a broken collarbone, and a third had teeth knocked out, said Kris Hermes of the group National Lawyers Guild.

He denied police allegations that protesters faked injuries by pouring red paint on themselves.

Police defended their tactics, saying the permit for the rally and march had expired, and the streets needed to cleared.

Officers were also defending themselves from assaults by protesters, Police Chief Garry McCarthy said.

The Occupy movement, which sprung up last year in New York and other US cities to protest against the unfair distribution of wealth between rich and poor, had been planning demonstrations in Chicago for several months.

But several officials in the city said the number of protesters arriving in Chicago to protest during the two-day Nato summit had been lower than many expected.

One reason may have been the decision to relocate a summit of the G8 leaders, held on Friday and Saturday, from Chicago to the presidential retreat at Camp David just north of Washington.

Some downtown Chicago businesses remained closed on Monday, the final day of the summit.