Bangui - Heavy weapons fire broke out on Sunday in the Muslim district of Bangui, the Central African Republic capital, during a referendum aimed at ending years of bloody sectarian strife, an AFP reporter said.
Fire from heavy machine-guns and rocket launchers erupted around a school where voters were waiting to cast their votes, prompting UN peacekeepers to move in to protect residents of Bangui's PK5 Muslim district.
A Red Cross staffer said six people were hurt.
Sunday's vote was seen as a test run for presidential and parliamentary elections due to take place December 27 to end more than two years of conflict between mainly Muslim and mainly Christian militias.
Five other people were hurt, two of them seriously, in the volatile Muslim-majority district earlier on Sunday.
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Another three were injured amid gunfire and grenade blasts in the district of Gobongo, a stronghold of the Christian "anti-balaka" militia, a security source said.
Several incidents were also reported in the country's north and east, said an unnamed source in the UN peacekeeping force, MINUSCA, sent in to quell fighting that has forced 10 percent of the population to flee the country.
If adopted, the constitution would usher in the country's sixth republic since independence from France in 1960 but mark its 13th political regime in as many years - underlining the chronic instability undermining the country.
The proposed constitution would limit presidential tenure to two terms, aims to fight institutional corruption and crimp the power of armed militias, blamed for years of chaos and terror.
The ballot comes two weeks after Pope Francis appealed to Muslims and Christians to live as "brothers and sisters".
Despite the presence of 11 000 UN and French peacekeepers, part of the impoverished country remains out of bounds, under the control of either rebel chieftains or bandits.
The widespread chaos hampered organisation of the ballot by the country's interim authorities, with few election posters visible on the streets just 48 hours beforehand.
Only 15 000 copies of the new constitution have been printed, meaning that few voters were fully aware of its contents.
Almost two million Central Africans have registered to vote in a population of 4.8 million - spurring hopes the election will be the first step in a return to peace and normalcy.
UN chief Ban Ki-moon appealed on the eve of the vote to ensure "that the referendum is conducted in a peaceful and credible manner" and called it a "significant milestone towards the end of the transition in the Central African Republic".
Many of the 5 600 polling stations are located in remote areas accessible only by dirt roads.
And of the 460 000 people displaced by the unrest living in camps across Central African Republic's borders - many of them Muslims - only 26% have been able to register.
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The country was plunged into its worst crisis since independence after longtime Christian leader Francois Bozize was ousted by rebels from the Seleka force in March 2013, triggering a wave of violence with "anti-balaka" militias.
Senior rebel figure Nourredine Adam had threatened to block elections in areas under his control.
His Patriotic Front for the Renaissance of Central Africa (FPRC), a splinter faction of the former Seleka rebel group that staged a coup in 2013, is staging an armed revolt in northern Kaga Bandoro.
The international community, which has been pouring aid into the country for over two years, is keen for the referendum as well as the follow-up elections to take place.
"These are make-or-break elections," said the International Crisis Group's Thierry Vircoulon.