Police arrested 71 abortion opponents Friday after they blocked a gate behind a women's clinic, chanting and singing to drown out a federal marshal's warning to disperse.

In the latest round of demonstrations, protesters also gathered at two other Buffalo clinics and a third clinic in a suburb.Police said charges were pending against the 71 people arrested and bused to an armory where 180 other abortion opponents are still being held. The 180 had failed to post bail after being arrested during a demonstration in suburban Amherst two days ago.

Friday was the fourth full day of continuing protests by the pro-life group Operation Rescue.

The group has targeted Buffalo for two to four weeks of demonstrations patterned after its siege of abortion clinics in Wichita, Kan. Those protests last summer led to 2,600 arrests.

Well before a Buffalo clinic on Main Street was scheduled to open Friday, about 70 abortion protesters blocked the gate behind it while approximately 50 others demonstrated across the street from the clinic's main entrance.

As a federal marshal read the injunction prohibiting abortion foes from blocking entrances to the clinic, those at the back entrance sat down and began drowning out the officer's words. The arrests began shortly before the clinic's scheduled 9 a.m. opening.