"The Turkish people have elected Erdogan as Turkey's first president/executive president under the new system. The Turkish people have said 'onwards' with President Erdogan," said Bekir Bozdag on Twitter.
Unofficial results show put Erdogan in the lead with over 95 percent of votes counted.
More than 56 million people were eligible to vote in Sunday's twin elections, held for the first time on the same day.
The vote ushers in a powerful new executive presidency, in line with constitutional changes narrowly approved in a referendum last year.
