U.S. Attorney General Eric Holder dispatched the U.S. Marshals Service to protect "appropriate people and facilities around the nation" in the wake of the murder of late-term abortion provider Dr. George Tiller in Wichita, Kansas on Sunday morning.

U.S. Marshals spokesman Jeff Carter, who confirmed the new security measures, told FOX News, "I can not disclose the subjects of our security efforts as it is the policy of the U.S. Marshals not to comment on the status of any protective detail."

Anti-abortion leaders voiced concern Sunday that the Obama administration and other Democrats may try to capitalize on the murder of Tiller to defuse the abortion issue in upcoming Supreme Court confirmation hearings.

Many anti-abortion groups condemned the killing of Tiller, a prominent abortion provider who was shot dead at his church in Wichita, Kansas. But they expressed concern that abortion-rights activists would use the occasion to brand the entire anti-abortion movement as extremist.

They also worried that there would now be an effort to stifle anti-abortion viewpoints during questioning of Supreme Court nominee Sonia Sotomayor. Her exact views on abortion aren't known, but conservatives fear she supports abortion rights.

Said the Rev. Patrick Mahoney, an anti-abortion activist: "No one should use this tragedy for political gain."

Tiller, one the few American doctors specializing in late-term abortions, had been the target of repeated protests and harassment for many years, and he was wounded by gunfire from an anti-abortion activist in 1993.

"It is abhorrent that once again, individuals who oppose the right to choose have used violence to try to advance their extreme anti-choice agenda," said Vicki Saporta, president and CEO of the National Abortion Federation.

"We condemn this lawless act of violence. The foundational right to life that our work is dedicated to extends to everyone. Whoever is responsible for this reprehensible violence must be brought to justice under the law," said Americans United for Life President and CEO, Dr. Charmaine Yoest, in a statement.

While many anti-abortion leaders swiftly issued statements condemning the shooting, their expressions of dismay were not echoed by Randall Terry, a veteran anti-abortion activist whose protests have often targeted Tiller.

"George Tiller was a mass murderer and we cannot stop saying that," Terry said. "He was an evil man -- his hands were covered with blood."

Terry said he was now concerned that the Obama administration "will use Tiller's killing to intimidate pro-lifers into surrendering our most effective rhetoric and actions."

A month ago, Terry was arrested protesting President Obama's appearance at the University of Notre Dame commencement. The president's graduation speech was dominated by abortion issue -- and an appeal for the nation to seek common ground instead of vitriol.

Mahoney said he had been conferring with other anti-abortion leaders about how to deal with any backlash to the Tiller killing that might undercut their cause at a time when they are trying to challenge Obama's support for abortion rights.

"I'd hope they wouldn't try to broad-brush the entire pro-life movement as some sort of extremist movement because of what happened in Wichita," Mahoney said. "That's really important -- don't use this personal loss for a political gain."

He noted that abortion is likely to be one of the most contentious issues at Sotomayor's confirmation hearings, and expressed hope that the Tiller murder would not be raised there.

Abortion rights leaders reacted to the killing with shock and determination

Nancy Keenan, president of NARAL Pro-Choice America, said the murder would "send a chill down the spines of the brave and courageous providers" offering abortion to American women.

"Violence and murder will never end the need for abortion," said Dr. Suzanne T. Poppema, board chair of Physicians for Reproductive Choice and Health. "With great sadness and discouragement we call on the government to reactivate its protection system for our nation's abortion providers."

Kim Gandy, president of the National Organization for Women, said Tiller was aware of the dangers he faced, "yet he continued to protect his patients and provide safe and legal abortions to women in often-desperate circumstances."

She and other activists urged that Monday be observed as a national day of mourning for Tiller, as well as a day of commitment to the cause of abortion rights.

According to the National Abortion Federation, Tiller was the eighth U.S. abortion provider murdered since 1977, and 17 others had been targeted with attempted murder.

The Associated Press contributed to this report.