WASHINGTON (AP) — The Justice Department approved Sirius Satellite Radio's $5 billion buyout of rival XM Satellite Radio on Monday, saying the deal was unlikely to hurt competition or consumers.

The deal was approved despite opposition from consumer groups and an intense lobbying campaign by the National Association of Broadcasters on behalf its AM and FM radio members.

"Weare astonished that the Justice Department would propose granting a monopolyto two companies that systematically broke FCC rules for more than a decade," said NAB Executive VP Dennis Wharton. "To hinge approval of this monopoly on XM and Sirius's refusal to deliveron a promise of interoperable radios is nothing short of breathtaking."

The buyout received shareholder approval in November. The companies said the merger will save hundreds of millions of dollars in operating costs—savings that will ultimately benefit their customers.

The Justice Department, in a lengthy news release explaining its decision, said the two companies compete not just with each other but also with other forms of radio and entertainment.

''The likely evolution of technology in the future, including the expected introduction in the next several years of mobile broadband Internet devices, made it even more unlikely that the transaction would harm consumers in the longer term,'' the Justice Department said. ''Accordingly, the division has closed its investigation of the proposed merger.''

In a statement, NAB Executive Vice President Dennis Wharton said: "We are astonished that the Justice Department would propose granting a monopoly to two companies that systematically broke FCC rules for more than a decade. To hinge approval of this monopoly on XM and Sirius's refusal to deliver on a promise of interoperable radios is nothing short of breathtaking."

XM Satellite shares rose $1.97, or 16.5 percent, to $13.90 in afternoon trading after the government's announcement while Sirius shares rose 28 cents, or almost 10 percent, to $3.18.