Residents in a collection of apartments and townhouses in Minneapolis are being warned about a gunman barging into homes and robbing them.

The warning came in a letter to residents last week who live in Heritage Park apartments and townhouses to the northwest of downtown on Olson Hwy.

“In the past few weeks we’ve had numerous reports from residents ... that an unknown masked suspect has been knocking on residents’ doors and forcing entrance at gunpoint,” the letter read.

The suspect has yet to harm anyone, the letter continued.

Police said there have been no arrests as of Sunday afternoon as “investigators are talking with victims and witnesses, and following up on leads,” said police spokeswoman Sgt. Catherine Michal.

Michal said that three robberies occurred on successive days, Sept. 24, 25 and 26, and all in the 8 p.m. hour. A similar crime at Heritage Park occurred about five weeks earlier and a bit later in the evening, she said.

The suspect’s face was concealed with a mask in one robbery and by “something else” in the other crimes, Michal said.

In one instance, the robber had a knife as well as a gun, Michal added. Taken from residents were credit cards, cash and a phone.

Heritage Park’s property manager has scheduled a community meeting for next week to go over the problem, the letter said, adding that a police representative will attend.

Until then, the letter directed residents “to keep your doors locked and only answer the door when you have confirmed that you know the individual.”

The letter did not mention any specifics about the suspect, including gender, ethnicity or age, who is preying upon those who live in the mixed-income development that once was a site of public housing, which was torn down in 1999.

Last week, Minneapolis was listed as the 25th most dangerous city in the country, according to a report published by 24/7Wall St.com, a news and opinion website. The city’s robbery rate was the 10th highest in the country, the rankings noted.