A landmark building in New York City across the street from the New York Stock Exchange is owned by a company with ties to a businessman targeted by U.S. sanctions, according to a new report.

The building at 23 Wall Street, constructed in 1914 and designated as a landmark in 1965, was recently used on Valentine's Day for a Prince concert and, earlier, was the location of the Gotham City Stock Exchange for "The Dark Knight Rises." It was the original headquarters of J.P. Morgan & Co. and was bombed in 1920 by anarchists, but now a developer wants to make it into an entertainment destination after years of vacancy.

A report released late Monday by the Africa Center for Strategic Studies, a U.S. Department of Defense think tank studying security issues across the continent, said the building is owned by an entity created by China Sonangol International Holding Ltd., a joint venture it said is 70%-owned by a Hong Kong-based syndicate. That syndicate, the report said, is run by Sam Pa, a man the U.S. alleged last year was an associate of Robert Mugabe's regime in Zimbabwe.

A call to Mr. Pa's cell phone by Risk & Compliance Journal seeking comment wasn't returned. Companies in the syndicate, which various analysts have called "88 Queensway Group" after the Hong Kong office address listed for many of its affiliate firms, couldn't be reached. China Sonangol didn't respond to a request for comment.

Neither Mr. Pa’s name, nor any of his alleged aliases, are on the corporate records of China Sonangol, according to the Africa Center report. However, a 2009 report by the U.S.-China Economic & Security Review Commission, a U.S. congressional panel, said "Xu Jinghua," which the U.S. government said is one of Mr. Pa’s aliases, "holds a leadership position within the '88 Queensway Group'" despite not being listed as a shareholder or a director at any of the group's companies. The same report listed China Sonangol as one of the companies in 88 Queensway group.

J.R. Mailey, the Africa Center report's author, said his allegation of Mr. Pa’s control of 88 Queensway Group is based on corporate and legal records, as well as interviews with former associates and friends of Mr. Pa.

"Sam Pa’s absence from the group’s corporate filings and his use of aliases create significant barriers to linking the group’s operations to him. This also makes it entirely possible that even some of the group’s partners, both in government and the private sector, have no clue with whom they are really dealing,” the report said.

The U.S. Department of Treasury, when placing sanctions on Mr. Pa in April 2014, alleged he gave more than $1 million, as well as supplies and equipment, to senior Zimbabwean officials to support the country’s intelligence service, which Treasury accused of being linked to pre-election intimidation. Mr. Pa also facilitated corruption by Zimbabwean government officials through illicit diamond deals, Treasury alleged at the time.

Mr. Pa, in an interview with Mr. Mailey cited in the report, said the allegations about his activity in Zimbabwe are "baseless."

“People are writing without grounds and without base,” Mr. Mailey quoted Mr. Pa as saying.

The Africa Center report said 23 Wall Street is owned by an entity called "CS Wall Street LLC." Risk & Compliance Journal confirmed, via New York City property records, that CS Wall Street bought 23 Wall Street, and the adjacent building, 15 Broad Street, for $150 million in 2008.

CS Wall Street is a Delaware-registered company the report said was created by China Sonangol as a vehicle for purchasing the building. (The Wall Street Journal reported in 2009 on the deal without naming CS Wall Street.) China Sonangol lists the building as one of its properties.

A Delaware registration agent for CS Wall Street didn't respond to requests for comment.

Ownership questions surrounding real estate are nothing new, as Risk & Compliance Journal discovered in September 2013 when investigating Manhattan property as an attractive destination for laundered money. But it took new prominence in recent months following a series in The New York Times that dove deep into the lack of transparency in the real estate market by focusing on the owners of condos in one Manhattan complex.

Those stories, among others, have shown how the real-estate industry isn't required to perform due diligence on prospective property buyers, opening the sector to money laundering and other risks.

For example, prosecutors have been targeting New York real estate when seizing assets, including a 36-story office tower at 650 Fifth Avenue, which a judge ruled in 2013 was subject to forfeiture by the U.S. after it alleged that one of the co-owners is a front for the Iranian government.

"When investors buy real estate using anonymous shell companies, it's virtually impossible to identify the true owners with any degree of certainty. This loophole has been exploited countless times by illicit entrepreneurs who seek to remain just beyond the reach of regulators and law enforcement," said Mr. Mailey, in an email.

Write to Samuel Rubenfeld at Samuel.Rubenfeld@wsj.com. Follow him on Twitter at @srubenfeld.