Two women cross the street after being brought out of a Planned Parenthood center following reports of an active shooter in Colorado Springs, Colorado, Nov 27, 2015. [Photo/Agencies]

Checking for explosives

Colorado Springs Mayor John Suthers said authorities were able to help guide the movements of officers through the building by watching live feeds from surveillance cameras mounted inside.

But a city police spokeswoman, Lieutenant Catherine Buckley, said it took officers a number of hours to establish communication with the suspect before he gave himself up.

"We did get officers inside the building. They were able to shout to the suspect and make communication with him and at that point they were able to get him to surrender and he was taken into custody," Buckley said.

An hour earlier, police said progress in securing the building was slowed by the fact that the gunman brought "some bags" with him into the clinic and left several items outside, all of which needed to be checked for possible booby traps or explosives.

After the arrest, Buckley said it would take hours more, and perhaps days, for investigators to fully process the crime scene.

CNN reported that investigators had located the suspect's car, and the vehicle would be searched for explosives.

Police swarmed the area around the building after an emergency call reporting shots fired at about 11:30 am Mountain Time (1830 GMT), and officers ultimately confronted the suspect inside the building, Buckley said.

Television footage aired by CNN showed a number of clinic staff and patients being escorted safely into police vehicles from the building, which lies on the northwest side of Colorado Springs, about 70 miles (112 km) south of Denver.

The FBI and agents from the US Bureau of Alcohol, Tobacco, Firearms and Explosives were assisting local law enforcement investigators.

US President Barack Obama was notified of the shooting by his Homeland Security adviser, Lisa Monaco, and "will be updated on the situation as necessary, a White House official said.