THE NATIONAL AIR and Space Museum in Washington was closed yesterday after anti-war demonstrators swarmed the building to protest a drone exhibit and security guards used pepper spray to repel them.

Smithsonian spokesman John Gibbons said a large group of demonstrators, estimated at 100 to 200 people, arrived at about 3 pm and tried to enter the National Mall museum.

When a security guard stopped group members from entering, saying they could not bring in signs, he was apparently held by demonstrators, Gibbons said. A second guard who arrived used pepper spray on at least one person and the crowd dispersed, he added.

A number of groups have been demonstrating in the city in the past week.

The group that arrived at the museum Saturday included individuals taking part in the October 2011 Stop the Machine demonstration in the city’s Freedom Plaza, which has an anti-war and anti-corporate greed message.

The group also included protesters affiliated with Occupy DC, a group modelled on the Occupy Wall Street protests in New York City.

A DC fire department spokesman said that medics treated or evaluated a dozen people at the scene but that no one was seriously hurt by the pepper spray.

Ann Wilcox, a lawyer working with Stop the Machine, said a 19-year-old woman was arrested by police. She paid a fine and was released.

The museum has an exhibit, Military Unmanned Aerial Vehicles, that covers the history of unmanned aircraft and their current use as offensive weapons.

The museum is expected to re-open today.