Microsoft Corp, Google Inc and Yahoo Inc agreed to a settlement worth $31.5 million to resolve accusations that the companies promoted illegal Internet gambling, the Justice Department said on Wednesday.

The companies were accused of receiving money from online gambling businesses to advertise illegal betting from 1997 through 2007.

As part of the settlement, the companies will pay cash to the U.S. government and provide millions of dollars worth of public service advertisements informing young adults and teenagers that Internet gambling is illegal.

U.S. Attorney Catherine Hanaway in St. Louis, Missouri, who prosecuted online gambling company BETonSPORTS Plc earlier this year, announced the settlement.

"These sums add to the over $40 million in forfeitures and back taxes this office has already recovered in recent years from operators of these remote-control illegal gambling operations," Hanaway said in a statement.

Microsoft will pay $4.5 million to the U.S. government, $7.5 million to the International Center for Missing and Exploited Children, and provide $9 million worth of public service advertising.

David Bowermaster, a Microsoft spokesman, said that Microsoft stopped accepting ads from online gambling sites nearly four years ago. "This agreement reflects our ongoing commitment to online safety," he said.

Yahoo's settlement of $7.5 million includes forfeiting $3 million to the U.S. government and providing $4.5 million worth of online ads for a public service advertising campaign. Google will pay $3 million, the department said.