MILAN, Jan 14 (Reuters) - Italian prosecutors confirmed on Friday that they were investigating Prime Minister Silvio Berlusconi over his dealings with a teenaged nightclub dancer.

In a statement, prosecutors said they had issued summons to Berlusconi and his lawyers in the case.

An investigation source told Reuters earlier on Friday that the probe included underage prostitution allegations.

The magistrates are also examining whether Berlusconi, who denies any wrongdoing, exerted improper pressure omn police officers to have the girl released when she was detained over theft allegations, the source said. (Reporting by Emilio Parodi)