Rwandans are going to the polls to vote on a referendum that would change the constitution and allow President Paul Kagame to run for as many as three more terms in office.
Friday's referendum asks for approval of an amendment that would shorten presidential terms to five years rather than seven.
But the amendment would make an exception for Kagame, allowing him to run for a third seven-year term and two more five-year terms after that.
Current law requires Kagame to step down at the end of 2017. If the referendum passes as expected, and he continues to win elections, he could stay in power until 2034.
Rwandans outside the country voted on the measure Thursday.
The 58-year-old Kagame, an ethnic Tutsi, commanded the rebel force that ended the Rwandan Genocide in 1994 and ousted Hutu extremists from power.
Kagame served as vice president and minister of defense under President Pasteur Bizimungu from 1994 until Bizimungu's resignation in 2000. Kagame has served as president since 2000.
He is popular inside Rwanda, but critics accuse him of suppressing free speech and having no tolerance for dissent. The United States and European Union have cautioned that allowing him to stay in power would undermine democracy.
The U.S. State Department said last month that Kagame should step down as scheduled and help "foster a new generation of leaders in Rwanda." The spokesman making the statement, Mark Toner, did not say what steps the U.S. would consider if Kagame tries to hold on to power.
Efforts by leaders in other African countries to extend their rule, including Burkina Faso, Burundi and Senegal, have led to violence.