Police Saturday night arrested dozens of Occupy Wall Street protesters who assembled in New York's Zuccotti Park to mark the six-month anniversary of the movement.

Activists staged a series of protests and demonstrations earlier in the day in Lower Manhattan, and at least 15 people were arrested, Reuters reported.

In the night, the protesters returned to the Zuccotti Park, where the Occupy movement began six months ago.

Some of the protesters began to erect tents in the park. Officers ordered them to leave, but they sat on the ground and refused to move.

They were then arrested and taken away in police vehicles. The park was cleared in less than 30 minutes. One woman who was arrested had difficulty in breathing and was taken away in an ambulance.

A New York Police Dept spokesperson said they were forced to arrest the protesters when they started breaking the park rules, the Associated Press reported.

See photos of the protests and arrests below.