Italy's Prime Minister Silvio Berlusconi resigned Thursday as president of AC Milan owing to the incompatibility of the two posts.

Berlusconi, 71, made the announcement through Milan's website hours after being sworn in for a fourth mandate at the head of the country's government.

The media mogul began his political career in 1994 as leader of the conservative party Forza Italia. He won the 2008 general elections in April at the helm of his new party, Popolo della Liberta.

Berlusconi owns Milan since 1986. He had to quit the club's presidency for two years in 2004 when a law preventing conflicts of interest for politicians was passed.