The Republic of Congo voted Sunday on constitutional changes that would allow President Denis Sassou Nguesso to seek another term.
The proposed amendments would abolish a two-term limit for presidents and an age limit of 70 for presidential candidates.
Results from the referendum are expected later this week. Opponents of the 71-year-old Nguesso had called for voters to boycott the referendum. Reports from the capital, Brazzaville, say turnout was low.
At least four people were killed during anti-referendum protests in the capital, Brazzaville, on Tuesday.
President Nguesso won disputed elections in 2002 and 2009, and has ruled Congo in different capacities for most of the past 36 years.
He is the latest in a string of African leaders who have tried to prolong their stay in office, often in the face of opposition protests.
Burkina Faso's longtime president Blaise Compaore was toppled by a popular uprising last year after parliament attempted to change term limits in the constitution.
Burundi's President Pierre Nkurunziza was elected to a third term in July but only after violent street demonstrations and a failed coup attempt.
The presidents of Rwanda and the Democratic Republic of Congo have also sought constitutional changes to stay in office.
Some material for this report came from AP, AFP and Reuters