The scene outside the church in Wichita where Dr George Tiller was shot dead
A prominent US abortion doctor has been shot dead at a church in the city of Wichita, Kansas.
Dr George Tiller, one of the few US doctors who performed late-term abortions, had been vilified by anti-abortionists in the US.
The gunman fled in a car, but officials say a suspect is now in custody.
US Attorney General Eric Holder said the US would offer protection to "appropriate people and facilities" in the wake of Dr Tillers' killing.
Dr Tiller's clinic - called Women's Health Care Services - had often been the site of demonstrations, and he had been shot and wounded by an assailant 16 years ago.
Questioning of the suspect, a 51 year-old man, is continuing. Wichita Deputy Police Chief Tom Stolz said he was likely to face one charge of murder and two counts of aggravated assault for allegedly pointing a gun at two other men.
Dr Tiller, who was 67, was shot just after 1000 (1500 GMT) at the Reformation Lutheran Church.
His lawyer, Dan Monnat, said his client was killed while serving as an usher during a morning church service. His wife was in the choir at the time.
Dr Tiller's widow, four children and 10 grandchildren issued a statement calling his killing "an unspeakable tragedy".
The statement said: "This is particularly heart-wrenching because George was shot down in his house of worship, a place of peace."
They said his death was a loss for Wichita and for women across America, saying he had dedicated his life to providing women with high-quality health care, despite frequent threats and violence.
Anti-abortion groups also denounced the shooting.
In a statement, Troy Newman of Operation Rescue said his group had worked for years through peaceful and legal means and through the proper channels to see Dr Tiller "brought to justice".
Oct 1998: Dr Barnett Slepian shot dead, Buffalo, New York
Jan 1998: Policeman killed in blast at clinic near Birmingham, Alabama
Dec 30 1994: Two receptionists shot dead at clinics near Boston
July 1994: Dr John Britton and a volunteer escort killed outside clinic, Pensacola, Florida
"We denounce vigilantism and the cowardly act that took place this morning."
Phill Kline, an opponent of Dr Tiller and a former attorney-general of the state of Kansas, said: "I am stunned by this lawless and violent act, which must be condemned and should be met with the full force of law."
President Barack Obama said he was shocked and outraged over the killing.
"However profound our differences as Americans over difficult issues such as abortion, they cannot be resolved by heinous acts of violence," Mr Obama said.
The shooting came two weeks after the president made a major speech on abortion at one of the main Catholic universities in the US.
Correspondents say the president is attempting to defuse the abortion issue - a highly emotive subject in US public life - by arguing that while it should remain legal, the government should do all it can to limit the number of unwanted pregnancies.
But members of the anti-abortion movement have been angered by the president's reversal of restrictions on federal funding for embryonic stem cell research and for family-planning groups which carry out or facilitate abortions outside the US.
Under Kansas state law, abortions later in pregnancy are legal only if two independent physicians agree that the mother could suffer irreparable harm by giving birth.
Dr Tiller's clinic is one of just three in the US to perform abortions after 21 weeks.
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