"Milo Djukanovic receives 54 percent of votes on the basis of processing 17.3 percent of the material," the Monitoring Center (CеMI) said.
The smallest of the republics of the former Yugoslavia elects the president for the seventh time since 1990, when a multi-party system was introduced here. Slightly over 1,200 voting locations were opened from 07:00 local time (05:00 GMT) to 20:00 (18:00 GMT).
The State Election Commission of Montenegro previously registered over 2,000 local and foreign observers, including representatives of the Organization for Security and Co-operation in Europe (OSCE) mission.
Seven candidates participated in the presidential race.
The second round of voting can be held in 14 days, if none of the candidates gets more than half of the vote.