A statement by the San Raffaele hospital in Milan said the hospitalisation was necessary after what it called a "cardiac deficiency".
Mr Berlusconi was Italy`s prime minister four times, but has since been convicted for tax fraud and bribery.
The leader of Forza Italia, who had a pacemaker implanted in a hospital in the US when he was 70, would undergo tests "in the next few days", the hospital statement said.
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