VIDEO: Relatives watch as Planned Parenthood shooting suspect appears in court

The man accused of killing three people at a Colorado family planning clinic has been told he will face first-degree murder charges.

Speaking in a raspy voice, Robert Dear made his first court appearance via a video link from the jail where he has been held since surrendering after Friday's five-hour siege.

The 57-year-old gazed downwards during most of the hearing in Colorado Springs as victims' relatives watched from a courtroom.

He is accused of shooting dead a university police officer who responded to the attack, as well as an Iraq war veteran and a mother-of-two inside the clinic.

Nine other people were wounded.

When asked by Judge Gilbert Martinez if he understood his rights, Dear replied: "No questions."

The clinic's parent organisation, Planned Parenthood, has said witnesses believe the gunman was motivated by his opposition to abortion.

But Dear has been described by acquaintances as a reclusive loner who did not seem to have strong political or social opinions.

Whatever authorities decide about his motive is sure to be controversial, given the political murkiness of Dear's statements and the debate over Planned Parenthood, which was reignited in July when anti-abortion activists released undercover video that they said showed the group's staff negotiating the sale of foetal organs.

Police have declined to speculate on a motive for the attack, but a law enforcement source said Dear told authorities "no more baby parts" during a rambling statement after being arrested.

Lawyer Daniel King, who represented Colorado cinema gunman James Holmes will act for Dear. Dear is expected to be formally charged on December 9.

After the hearing, district attorney Dan May said Dear could face other charges, but did not elaborate.

El Paso County Coroner's Office has said the shooting victims - 35-year-old Jennifer Markovsky, Ke'Arre Marcell Stewart, 29, and Garrett Swasey, 44 - each died from a gunshot wound.

Mrs Markovsky's husband Paul said his wife was caring and compassionate and a patient and understanding parent.

He released a statement saying she was deeply loved by everyone who knew her, he remembered her reading to their children and helping them with their homework, and would miss her cooking, crafting and adventurous spirit.

Meanwhile police records show that Dear was accused of sexually assaulting a woman in South Carolina in 1992.

He was arrested in North Charleston on a charge of criminal sexual conduct after a woman said he held a knife to her neck, forced her into her apartment and sexually assaulted her after hitting her in the mouth. No records show how the case was ultimately handled.

Investigators said Dear told them he knew the woman and had consensual sex with her.

Little information about Dear's background has been released and documents in the Colorado Springs case have been sealed.