An attack on a Catholic mission sheltering some 20,000 refugees in the Central African Republic left over 40 people dead and forced thousands to flee this week, according to the UN and local officials. 

The attack happened on Thursday in Alindao, a town 300 kilometers east of the capital Bangui. 

"We have counted 42 bodies so far, but we are still searching for others. The camp has been burnt to the ground and people fled into the bush and to other IDP (internally displaced person) camps in the city," Alindao lawmaker Etienne Godenaha told Reuters.

A humanitarian source confirmed that more than 40 people were killed.

The UN meanwhile said that thousands of people were forced to flee when the mission was set on fire.

"This vicious cycle of repeated attacks against civilians is unacceptable," the UN humanitarian coordinator in the Central African Republic, Najat Rochdi, said in a statement.

Thousands have died and a fifth of the country's 4.5 million population have fled their homes in a conflict that broke out after mainly Muslim Seleka rebels ousted President Francois Bozize in 2013, provoking a backlash from Christian anti-balaka militias.

Despite electing a new leader in 2016, the country has continued to face political instability and tit-for-tat inter-communal violence.