An alligator was killed as it was removed from a creek in the US state of Florida along with a 41-year-old woman's body, officials said Saturday.

Police said they had responded to a report of a body seen in the creek in Largo, Florida, and that the 13-foot, 8.5-inch (4-meter) male alligator was "humanely killed" on Friday.

Officers identified the body on Saturday, but said "the manner and cause of death is pending," and that the investigation was ongoing.

Witness Jamarcus Bullard told US media that he saw a big alligator and a body in the creek, and ran to a nearby fire station to report it.

"I threw a rock at the gator, just to see if it was like really a gator," Bullard told WFLA-TV, an NBC News affiliate, on Friday. "It pulled the body, like it was holding on to the lower part of the torso, and just pulled it under the water."

Bullard said the alligator put up a strong fight against authorities.

"They put a rope around its neck and put it on a pulley of a truck," he said. "They were reeling it in, but it started to pull the truck into the water.

"They got this long stick thing, pulled the head out of the water, then they shot it and once they reeled it all the way out, they stretched it out and measured it 13 feet long and they shot it again," Bullard said.

Alligators are common in the southeast United States, especially in Florida.

In July, a 69-year-old woman was killed by an alligator near a lagoon in South Carolina, with police saying the animal guarded her body and kept rescuers back.