The United Nation's children agency has called on rebels and pro-government groups in the Central African Republic (CAR) to stop recruiting children to fight in the country's conflict that has seen armed opposition groups seize key towns.

"Reliable sources have informed us that children are newly being recruited among their ranks," Souleymane Diabate, a UNICEF spokesperson in CAR, said in a statement on Friday.

UNICEF condemned the involvement of boys and girls "who may be forced to fight, carry supplies, perform other support roles and be abused as sex slaves by armed groups".

It said that even before the current conflict erupted last month, about 2,500 children were associated with multiple armed groups, including self-defence groups, in CAR.

Shannon Strother, the UNICEF emergency coordinator in CAR, told Al Jazeera that the organisation fears that the country's new conflict has seen a rise in child soldiers.

"What we have is a series of credible reports from multiple sites across the country that children are being armed forces, including in Bangui," she said.

"Since 2007 we have been able to negotiate the release of 1,300 children, but we are concerned with this new conflict we will see a rise in children with armed groups."

Widespread violence

More than 300,000 children have been affected by the violence in the country and its consequences, including through recruitment, family separation, sexual violence, forced displacement and having no or limited access to education and health facilities, it said.

"We are very concerned about children that might have possibly been displaced and separated from parents, but also we are concerned about children that are living on the streets and those that have been associated with those armed groups," Strother added.

Meanwhile, the United Nations humanitarian agency (OCHA) has also voiced serious concerns about the protection of civilians amid reports of widespread looting and violence.

An estimated 316,000 people are living in the affected areas, and about 700,000 others in Bangui are at further risk of an escalation in fighting, it said in its latest situation report.

The Seleka rebel coalition's lightning three-week advance from the north of the country to within striking distance of Bangui has raised fears of a spreading crisis and drawn regional calls for peace negotiations.