The man charged with killing a prominent abortion provider claimed Sunday that more violence is possible as long as the medical procedure is allowed to continue, giving his warning in calls that also focused on complaints about his treatment in jail.

Scott Roeder, being held on charges of first-degree murder and aggravated assault in the killing of Dr. George Tiller one week ago, called The Associated Press from the Sedgwick County jail.

Tiller, whose Wichita clinic was among only a few in the U.S. performing third-trimester abortions, was shot while serving as an usher at the Lutheran church he attended.

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"I know there are many other similar events planned around the country as long as abortion remains legal," Roeder said.

He would not elaborate.

Tiller's clinic in Wichita had been a target of regular demonstrations by abortion opponents. Most were peaceful, but his clinic was bombed in 1986 and he was shot in both arms in 1993. In 1991, a 45-day "Summer of Mercy" campaign organized by the anti-abortion group Operation Rescue drew thousands of protesters to Wichita, and there were more than 2,700 arrests.

Jim Cross, a spokesman for the U.S. attorney's office, did not have an immediate comment Sunday on Roeder's statement.

The Justice Department opened an investigation Friday to see if the gunman who killed Tiller had accomplices. The DOJ said its Civil Rights Division and the U.S. attorney's office in Kansas will seek to determine if the killing violated a 1994 law creating criminal penalties for violent or damaging conduct toward abortion providers and their patients.

An attorney for the Tiller family, Dan Monnat, said he was not sure they should be dignifying Roeder's actions and threats with a response "every time he makes a hare-brained phone call."

"I am hopeful that state and federal authorities, including homeland security, will give Mr. Roeder and his information a deserving response," Monnat said, declining to elaborate.

Hundreds of mourners attended Tiller's funeral on Saturday. Most anti-abortion groups avoided the service, having denounced Tiller's shooting.

Roeder, a 51-year-old abortion opponent, was arrested a few hours after the shooting just outside Kansas City.

He told the AP he refused to talk to investigators when he was arrested, and has made no statements to police since then.

"I just told them I needed to talk to my lawyer," Roeder said.

Asked if he shot Tiller, Roeder replied that he could not comment about that and said he needed to clear everything with his lawyer.

In two separate calls to AP on Sunday morning, Roeder was far more talkative about his treatment at the Sedgwick County jail, complaining about "deplorable conditions in solitary" where he was kept during his first three days there.

Roeder said it was freezing in his cell. "I started having a bad cough. I thought I was going to have pneumonia," he said.

He said he called AP because he wanted to emphasize the conditions in the jail so that in the future suspects would not have to endure the same conditions.

Roeder also said also wanted the public to know he has been denied phone privileges for the past two days, and needed his sleep apnea machine.