A man suspected of fatally shooting a Kansas doctor who performed abortions was in jail Monday while investigators sought to learn more about his background, including his possible connections to anti-abortion groups.

George Tiller, 67, was serving as an usher during morning church services Sunday when he was shot in the foyer of Reformation Lutheran Church in Wichita, police said. The gunman fired one shot at Tiller and threatened two other people who tried to stop him.

The suspect, identified by one law enforcement agency as Scott Roeder, was taken into custody some 270 kilometres away in a Kansas City suburb about three hours after the shooting.

At a news briefing Monday morning, Wichita authorities confirmed that charges had not yet been filed and said they were not releasing any new information. The FBI also has been investigating, and it was not clear if charges would be filed in state or federal court.

Tiller had been a lightning rod for abortion opponents for decades. The women's clinic he ran is one of three in the nation where abortions are performed after the 21st week of pregnancy, when the fetus is considered viable, and has been the site of repeated protests for about two decades.

A protester shot Tiller in both arms in 1993, and his clinic was bombed in 1985.

Roeder, 51, was taken to Wichita and was being held without bail on one count of first-degree murder and two counts of aggravated assault. Formal charges were expected to be filed Monday.

Outside the clinic Monday morning, flowers were placed along a fence, and the anti-abortion group Kansas Coalition for Life left a sign saying members had prayed for Tiller's change of heart, "not his murder."

In Washington, the U.S. Marshals Service said that as a result of Tiller's shooting, Attorney General Eric Holder had ordered it to "increase security for a number of individuals and facilities." It gave no details.

Tiller himself last had protection from the U.S. marshals in 2001, and he and other doctors received such protection at different times in the 1990s.

A man with the same name as the suspect has a criminal record and a background of anti-abortion postings on sympathetic websites.

In one post written in 2007 on the website for the militant anti-abortion group Operation Rescue, a man identifying himself as Scott Roeder asked if anyone had thought of attending Tiller's church to ask the doctor and other worshippers about his work.

"Doesn't seem like it would hurt anything but bring more attention to Tiller," the post said.

But police said Sunday that all early indications showed the shooter acted alone.

Wichita Deputy Police Chief Tom Stolz said Tiller apparently did not have a bodyguard with him in church, although the doctor was routinely accompanied by one.

An attorney for Tiller, Dan Monnat, said the doctor's wife, Jeanne, was in the choir at the time of the shooting.

The last killing of an abortion provider was in October 1998 when Dr. Barnett Slepian was fatally shot in his home in a suburb of Buffalo, N.Y. A militant abortion opponent was convicted of the murder.