The current prime minister of the self-proclaimed Donetsk People's Republic in eastern Ukraine, Alexander Zakharchenko, is leading in Sunday's elections with 70 percent, the republic's Central Election Commission said after tallying 50 percent of the ballots.
Zakharchenko's Donetsk Republic party is also leading in the parliamentary elections with more than 60 percent.
The Donetsk Central Election Commission said that more than one million people voted in the elections.
In April, Ukrainian authorities launched a military operation in the country's southeast, where independence supporters refused to accept the new government that was put in power following a coup in February.
The political discontent led Donetsk and Luhansk regions in eastern Ukraine to hold referendums this May on self-determination. Over 90 percent of the voters cast their votes for greater autonomy. The territories declared themselves sovereign states as a result.
The European Union and the United States said earlier the elections would violate the Minsk agreement on the regulation of the crisis in Donbas, and that the international community would not recognize them.
Meanwhile, Russia expressed its intention to recognize the elections in the self-proclaimed people's republics, saying that the not recognizing of the elections would instead run counter to the Minsk protocol and disrupt the progress towards finding a sustainable political solution to the conflict.