DENVER -- Denver police say four women who were out walking, jogging or listening to their iPods last week were assaulted by a man who groped them on their backside.

"We need to let the community know that he's out there so they can protect themselves," said department spokesman Sonny Jackson.

The assaults happened Friday and Saturday in an area bounded by York Street and Speer Boulevard and by First and 13th Avenues.

Jackson acknowledged that some people might be hesitant to report such an assault, but he said it's important that they do so.

"First off, you don't have the right to touch anyone without their permission," Jackson said. "The law is absolutely clear on that."

Jackson said the sooner a victim reports the crime, the easier it is to try to locate the assailant.

Neighborhood resident Sharon Gatliffe told 7NEWS that she was surprised to learn of the attacks.

"I feel really safe here," she said.

Another resident, Christa Rook, said it's important to know about the assaults and to report them.

"I would call police if it happened to me. I would consider it my responsibility to protect other women out there," Rook said.

"I would definitely call police because these things can escalate and everybody should be aware of what's going on," Gatliffe said.

Jackson told 7NEWS that there was a similar assault on April 8, but investigators don't know if it was the same man.

The department released a sketch of the assailant Tuesday. Police describe him as a stocky Hispanic, 5 feet 5 inches to 5 feet 9 inches tall, black possibly spiked hair, and a possible mustache.

They say he is about 22 to 26 years old and that he speaks with a Spanish accent.

Capital Hill resident Tristan Swartz told 7NEWS that women can do several things to try to protect themselves.

“It’s never a bad idea to go to the other side of the street,” Swartz said. “You can pick up your cell phone and act like you’re making a call. Look right at them and make sure they know that you know they’re there. If you need to, step into a store for a second to let them go by.”

Jackson said anyone who knows anything about these assaults is asked to contact Denver police.