Voters in Rwanda went to the polls to decide on a draft constitution that supporters say promotes democracy and will help curb the ethnic extremism that sparked the 1994 genocide.
Nearly 95 percent of Rwanda's four million eligible voters have cast ballots in the country's first constitutional referendum.
The chairman of Rwanda's National Electoral Commission, Chrysologue Karangwa, said the votes will be counted at more than 1,500 polling stations, and preliminary results could be announced as early as Tuesday.
"We do not have any problems in the polling," he said. "We have independent observers. There are about 966. We have 60 international observers. This referendum is very important to our country because it is the fundamental role from which the country is going to build."
Rwanda's transitional parliament adopted the draft constitution in April. The charter paves the way for multi-party presidential and parliamentary elections, possibly as early as July.
Supporters of the draft say much of the constitution is designed to heal the ethnic divisions between Rwanda's minority Tutsi and majority Hutu populations. In 1994, Hutu extremists killed nearly a million Tutsis and moderate Hutus. The slaughter ended when the Tutsi rebel army under Paul Kagame overthrew the Hutu extremists and set up a transitional government.
The draft constitution forbids political parties from identifying themselves around an issue, such as race or ethnicity, that could divide the Rwandan people.
It also attempts to limit one-party domination in government by stipulating that the president, the prime minister and president of the lower house of the two-chamber parliament may not be members of the same political party.
Nevertheless, critics say, there are elements in the constitution that clearly favor President Kagame's ruling Rwandan Patriotic Front. They note that one article in the constitution prohibits political parties from organizing at grass roots level. This, the critics say, gives the ruling party a huge, unfair advantage.
If voters approve the new constitution, it will replace an interim framework Mr. Kagame put in place in 1994. In 1999, his transitional government extended its mandate for another four years.