Groups opposed to abortion protested at numerous Planned Parenthood offices across the U.S. on Aug. 21, as part of a nationwide effort to draw attention to the organization. (AP)

Thousands of antiabortion activists descended upon Planned Parenthood clinics on Saturday to participate in a nationwide protest aimed at cutting off federal funding for the controversial health-care organization.

The demonstrations unfolded at about 320 clinics around the nation, according to organizers, with some gatherings drawing a few dozen protesters and others drawing hundreds and perhaps thousands more.

The protests kicked off at 9 a.m. Saturday and included speakers, prayer groups and chants, as well as signs distributed by organizers that said “Planned Parenthood sells baby parts.”

The protests come after an antiabortion group secretly filmed a series of videos that show Planned Parenthood staffers discussing the extraction of fetal tissue from aborted fetuses before it is sent to research facilities. Abortion opponents claim the video captures an illegal operation in which organs are harvested for money, but Planned Parenthood officials have claimed the videos were edited to bolster critics’ false claims, according to the Associated Press.

“These rallies are meant to intimidate and harass our patients, who rely on our nonprofit health centers for basic, preventive health care,” Eric Ferrero, vice president of Planned Parenthood, said in a statement. “The people behind these protests have a clear political agenda: They want to ban abortion, and block women and men from accessing basic reproductive health care.”

Though the official number of protesters was not immediately available, organizers billed the effort as the largest-ever rally against the health-care provider. Monica Miller, the director of Citizens for a Pro-Life Society, one of the participating groups, told USA Today that previous protests have drawn thousands of protesters, but hundreds of simultaneous protests have never taken place on the same day.

“We want to draw attention to the injustice of legalized abortion,” she said. “The American public needs to be awakened to the atrocity of what is happening to innocent unborn children.”

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