ROME - Both Italy's euroskeptic, populist Five Star Movement (M5S) and anti-immigrant League party on Monday claimed the mandate to form the next government, the parties' leaders announced on Monday.

Partial official data showed no single party, nor coalition alone will have enough seats in parliament to govern.

At least 73 percent of Italy's 46.5 million voting age citizens turned out on Sunday elections to decide who would occupy the 315-member Senate and the 630-member Lower House.

Halfway through an interior ministry vote count on Monday, the center-right coalition led by media mogul Silvio Berlusconi scored close to 38 percent in the Senate and 37 percent in the House.

However, the right-wing, euroskeptic and anti-immigrant League, pulled ahead of Berlusconi's party, prompting its leader Matteo Salvini to claim victory.

With almost all votes counted, official data showed the M5S was the largest single party with 32 percent. The vote marked "a triumph" for the Five Stars, which were the absolute winner of the contest, according to its leader Luigi Di Maio.

Any party or coalition would need to make further coalitions to reach the absolute majority in parliament.

Di Maio, 31, stressed the M5S emerged from the vote as "a force representing the nation entirely... which cannot be said about other political forces."

It was a mention to Matteo Salvini's League, which scored the second best result on Sunday. In fact, despite running in the election as a national force -- and dropping the adjective "Northern" from its name -- the League has its original roots in Italy's northern regions.

Di Maio took pains to reassure "international observers, investors, Europeans and Italians" that the Five Star Movement can be trusted, adding that "we are open to debate with all political forces."

The big loser was the Democratic Party of outgoing Prime Minister Paolo Gentiloni, which dipped below 20 percent in both houses of parliament and came in at just over 20 percent in combination with its smaller allies.

This prompted speculation that its leader and former Italian prime minister Matteo Renzi, who is set to hold a press conference later on Monday, may step down.