Four people were killed by mobs in Central African Republic's capital Bangui on Thursday, witnesses said, in escalating religious violence that could threaten a December election.

That brings this week's death toll to 11, including three senior negotiators for the Muslim Seleka alliance visiting the capital for peace talks aimed at resolving a two-year conflict.

The spike in violence might wreck plans to hold long-delayed elections this year, as former colonial power France and other Western countries push for an end to a transition period. The electoral commission on Wednesday set Dec. 13 as the date for both presidential and parliamentary elections.

Witnesses say three Muslims were attacked early on Thursday as they left the city's only Muslim enclave, PK5, to enter the Christian sixth district.

Two of them were killed immediately and their bodies chopped into small pieces, witnesses said. A third man escaped but was then stoned to death by a crowd and his body left by a church, the witnesses said.

"I am shocked by what I saw," said a woman from the sixth district, who asked to remain anonymous. "Even children were stoning the man who moaned and begged for mercy before dying."

In an apparent act of retaliation, a Christian was killed later in the morning as he entered PK5, according to residents and family members visiting his body in the morgue.

Mostly-Muslim Seleka rebels seized power in the majority Christian nation in a coup in 2013, prompting lethal reprisals by Christian militias known as anti-balaka.

Muslim and Christians have since split into segregated communities across the landlocked country. Tens of thousands of Muslims have fled to the far north, creating defacto partition.

Despite the presence of thousands of U.N. peacekeepers (MINUSCA), violence has flared again in Bangui in recent weeks, sparked by the murder of a Muslim man. More than 80 people have been killed.

On Thursday, hundreds of protesters blocked a main road in the capital to denounce the violence while residents fled Christian neighborhoods to avoid further reprisal attacks.

U.N. spokesman Stephane Dujarric said this week that five staff members had been attacked in their homes, leaving one person injured.

"We call for restraint to ensure that recent unfortunate events will not lead to a larger drama...," said U.N. Special Representative Parfait Onanga-Anyanga this week.

(Writing by Emma Farge; Editing by Louise Ireland)