Microsoft, Yahoo and Google agreed to pay a total of 31.5 million dollars to settle a government probe into their role in promoting online gambling dating back to 1997, officials said Wednesday.

The settlements marked the latest development in a US crackdown on Internet gambling, which has attracted a large number of Americans using offshore gaming websites.

The Microsoft settlement totals 21 million dollars, including 4.5 million to the United States and a 7.5 million-dollar contribution to the International Center for Missing and Exploited Children, the Justice Department said in a statement.

Microsoft also agreed to provide a nine million-dollar campaign aimed at showing young Web users that online gambling is illegal under US law.

Google agreed to pay three million dollars to settle similar charges and Yahoo 7.5 million and to fund an online public service campaign discouraging online gambling.