By Baris Gundogan and Mehmet Tosun
The main opposition Republican People's Party (CHP) presidential candidate would hold a news conference on election results at the party's headquarters in Ankara on Monday.
According to a statement by Muharrem Ince's election office, Ince will speak at 12.00 p.m. local time (0900GMT).
Earlier on Sunday, President Recep Tayyip Erdogan declared his success in Turkey's historic presidential and parliamentary elections.
Some 98.9 percent of ballot boxes in the presidential polls have so far been opened.
According to unofficial results, Ince received 30.69 percent of the votes.
Following the unofficial results, CHP spokesman Bulent Tezcan, in a press meeting, warned the nation against any provocations.
Tezcan also said their “greatest wish” is the election process be completed without "any tragic incident", adding that his party would "continue its struggle on the democratic ground regardless of the outcome [of the elections]."