ROME - An Italian protest party said its website had come under a "hacker attack" that would force it to hold a new online poll among its members on Friday to identify possible candidates for president.

"The voting on the president yesterday came under a hacker attack," the Five Star Movement led by former comedian Beppe Grillo said on its blog.

"We have therefore decided to cancel yesterday's vote and hold a new one today with higher levels of security," the statement said.

The top 10 names selected will be voted on again on Monday to come up with the party's candidate for president, which in Italy is elected by parliament.

The party said earlier that the country's two-main political forces -- the center-right and centet-left -- were deciding on candidates in "secret rooms" and said it wanted "a public and democratic consultation".

Among the possible names mentioned by M5S supporters on social media was Gino Strada, the outspoken head of the international medical charity Emergency, and Milena Gabanelli, an investigative journalist on public television.

A joint session of parliament is due to meet to begin voting for a new president on Thursday.