The two girls, ages 15 and 17, were arrested as they were writing messages with chalk on the sidewalk in front of the hotel where Democratic presidential nominee Sen. Barack Obama of Illinois was staying during the party's convention, Christian Newswire reported. Operation Rescue claimed police knocked the girls to the ground and kneed them in their backs before the two were handcuffed.

Also arrested was the Rev. Patrick Mahoney of the Christian Defense Coalition, who said the group received permission for the chalking activity from city officials. Mahoney said the group had been "sidewalk chalking" for six days before Wednesday's arrests without incident.

"I am shocked at how cowardly these police officers behaved by attacking little girls without warning or provocation," said Operation Rescue President Troy Newman, who also called for disciplinary action against the officers involved in the incident.

"Operation Rescue spent the week participating in 'A Prayer For Change' with Reverend Mahoney and these young people, who have conducted themselves peacefully and appropriately at all times," Newman said.