In a full-page ad, a mysterious group called out Minnesota's congressional delegation on gun control measures and on donations from the National Rifle Association.

The ad in Monday's Star Tribune was sponsored by a group calling itself "Listen to the Children," but it was unclear who exactly was behind the ad.

Addressed to Washington policymakers, the ad asked if they would introduce, cosponsor or vote for legislation to ban the manufacture and sale of high-capacity magazines for firearms, and if they would return any donation from the NRA and its affiliates and refuse to accept future NRA donations. The ad announced that the politicians' answers will be printed in another ad in the Star Tribune in one week and noted that those who didn't answer will be considered as responding "no" to the two questions.

The ad comes just two days after 20,000 Minnesota students and adults rallied at the State Capitol, joining hundreds of thousands of protesters in D.C. for the March for Our Lives event. Participants pushed for stricter gun control in the wake of the Parkland, Fla., high school shooting that killed 17 kids and staff members in February.

It's unclear who is connected to Listen to the Children, which published a Minneapolis P.O. box address in the ad. According to public records, the nonprofit filed with the state Secretary of State's office on March 9 and lists a St. Paul business address and CT Corporation System Inc. as a registered agent. The nonprofit also lists Ellen Durkin, a paralegal at the Minneapolis-based law firm Gray Plant Mooty, as the incorporator. Messages left with Durkin weren't returned Monday. In response to a reporter's request, the Star Tribune advertising department declined to identify who paid for the ad, citing confidentiality in ad agreements.

The ad is addressed to Minnesota's U.S. delegation: Demo­cratic Sens. Amy Klobuchar and Tina Smith; Democratic Reps. Tim Walz, Betty McCollum, Keith Ellison, Collin Peterson and Rick Nolan; and Republican Reps. Jason Lewis, Erik Paulsen and Tom Emmer.

McCollum, Klobuchar and Smith posted on Twitter on Monday, saying they supported a ban on high-capacity magazines and that they haven't accepted money from the NRA. Nolan's office said that he would also support the legislation and has never received money from the NRA. A spokesman for Walz said he co-introduced this year's assault weapons ban, including the ban on high-capacity magazines, and stated that Walz has donated all past NRA contributions to the Intrepid Fallen Heroes Fund, which supports military personnel and their families, and won't accept future contributions.

A spokesman for Paulsen said he's supported ways to combat gun violence, but he didn't specifically address high-capacity magazines or NRA funding. Paulsen, who has taken campaign contributions from the NRA in the past, said Monday he would not rule out doing so in the future. "I wouldn't discount it, but I would certainly scrutinize it," he said. Messages left with Lewis, Ellison, Emmer and Peterson's offices weren't returned Monday.

Staff writer Jessie Van Berkel contributed to this report.

Kelly Smith • 612-673-4141