Heavy gunfire has broken out in a Muslim district of the Central African Republic's capital, Bangui, during a referendum on a new constitution.

UN forces deployed after machine-gun fire and rocket launchers were used, as voters waited near a school.

It is hoped the new constitution can help end more than two years of conflict in the CAR between Muslims and Christians.

Presidential and parliamentary elections are also due on 27 December.

The conduct of the referendum is seen a test of whether December's elections can go ahead safely, correspondents say.

Several people were reported to have been injured in the latest violence in the PK5 district of Bangui, but it is not yet clear who carried out the attack.

An earlier incident left several others wounded.

There were also reports of grenade explosions in the city's Gobongo district, with three wounded according to a security source quoted by AFP.

The CAR has been prey to sectarian violence since March 2013 when Muslim Seleka rebels briefly seized power, deposing the Christian President Francois Bozize.

The Seleka group was then itself ousted, leading to a wave of violent reprisals against the Muslim population by the Christian anti-Balaka militia.

A breakaway faction of the Seleka group has called for a boycott of December's elections, saying conditions are not right for a fair vote.

Thousands have been killed and hundreds of thousands displaced since 2013.

Eleven-thousand UN peacekeepers are deployed in the CAR.

Some two million people have registered to vote, just under half the population.

Only two weeks ago, Pope Francis visited the country and appealed to Muslims and Christians to live in harmony.