Iran's reformist President Hassan Rouhani has decisively won the country's presidential election, according to official results, fending off a challenge by principalist rival, Ebrahim Raisi.

With all of votes in Friday's poll counted, Rouhani was re-elected with 57 percent, Interior Minister Abdolreza Rahmanifazli said on Saturday.

"Of some 41.2 million total votes cast, Rouhani got 23.5 ... and won the election," Rahmanifazli said in remarks carried live by state TV.

Raisi, Rouhani's closest rival, got 15.8 million votes, he added.

A big turnout on Friday led to the vote being extended by several hours to deal with long queues.

Agencies