The United Nations has warned groups carrying out atrocities in the Central African Republic that the world is watching and will hold them to account, after the killings of hundreds of people, mainly civilians.

The warning from UN Secretary-General Ban Ki-moon on Friday came a day after a militia killed 27 Muslims in a village outside the capital, Bangui.

"Too many people are scared and the country is on the brink of ruin ... The bloodshed must stop," Ban said in a radio address to the nation.

"I have a clear message to all who would commit atrocities and crimes against humanity. The world is watching. You will be held to account," he added.

The International Criminal Court has said all parties could be investigated.

Sectarian violence

CAR has been paralysed by cycles of violence since mainly Muslim Seleka rebels ousted President Francois Bozize in March. Their months in power have been marked by killings, looting and other abuses, leading to the emergence of Christian militia opposed to them.

We have noticed several cases of traumatised people, a few cases of survivors of gender-based violence, and also a few cases of separated children [from] their families.

Maurice Azonnankpo ,
UNHCR

These militia and gunmen loyal to Bozize attacked the capital last week, triggering fresh killings and reprisals that have deepened the sectarian conflict.

More than 600 people have been killed and 159,000 displaced in the fighting, according to the UN's refugee agency.

"We have noticed several cases of traumatised people, a few cases of survivors of gender-based violence, and also a few cases of separated children [from] their families," UNHCR's Maurice Azonnankpo told Al Jazeera from CAR.

"We have our teams at all the [internally-displaced persons] sites where they are conducting distribution of non-food items... to respond to the needs of these IDPs in Bangui."

French Defence Minister Jean-Yves Le Drian also warned of rising violence as he met some of the 1,600 French troops deployed in Bangui.

"The spiral of confrontation has abruptly worsened," Le Drian said, warning of "the early beginnings of a humanitarian crisis".

A week after France sent troops into its former colony to bolster an African peacekeeping force, bands of armed thugs continue to roam the streets, and heavy bursts of gunfire still ring out intermittently.

A senior African Union official told Reuters news agency on Friday that the AU had authorised an increase in the force deployed to CAR from 2,500 to 6,000 troops.

"The decision by the Peace and Security Council (PSC) is to authorise us to increase the force. We can go up to 6,000, depending on the needs," El Ghassim Wane, the director of the AU's Peace and Security department, said.

For the latest news from Central African Republic, follow Al Jazeera's Tristan Redman and Nazanine Moshiri, who are on the ground in CAR, on Twitter.

Source: Al Jazeera and agencies