Bangui - Heavy gunfire, a grenade and threats of violence in Central African Republic on Sunday prevented some residents from voting in a constitutional referendum to move the country toward stability.The vote on a new constitution adopted by the transitional government comes two weeks after a visit by Pope Francis, who called for peace and reconciliation between the country's Christian and Muslim populations."It's since last night that these extremists have taken us hostage. They have distributed ammunitions to their elements to use all day Sunday to prevent the vote," said Ousmane Abakar, a Muslim community leader in the PK5 neighbourhood in the capital, Bangui.Residents in the northern Gobongo neighborhood of Bangui said a grenade exploded near a voting centre, injuring three people. In Kaga Bandoro in the country's north, an armed group threatened to kill people who went to vote.The referendum for a planned 2 million people in more than 5 500 stations continued elsewhere, though there were reports of missing voter cards. Presidential and legislative elections are scheduled for December 27.Ban calls for peaceful voteIf approved by voters, the new constitution will create a Senate and safeguard for freedom of worship and religious freedoms.United Nations Secretary-General Ban Ki-moon called for a peaceful and credible vote."The referendum is a significant milestone towards the end of the transition in the Central African Republic which will lay new foundations for a stable future for the country and its people," he said in a statement.Central African Republic descended into conflict in 2013 when Muslim rebels overthrew the Christian president. That ushered in a brutal reign in which Muslims committed atrocities.When the rebel leader left power the following year, a swift and horrific backlash against Muslim civilians followed in which Muslims were killed in the streets and sectarian violence has continued.