Forces allied to renegade General Laurent Nkunda pose a serious threat to stability in eastern Democratic Republic of Congo, the UN says.
Laurent Nkunda studied psychology at university
UN peacekeeping head Jean-Marie Guehenno has called for international pressure to help end the violence.
Gen Nkunda has been leading a rebellion in the east against the government.
Some 165,000 people have fled clashes between government forces and rebels since Gen Nkunda agreed to integrate his forces into the army in January.
Last year's historic elections, which saw Joseph Kabila elected president, were supposed to mark the end of years of conflict and mismanagement in DR Congo.
"There is concentration of armed forces from both sides but what is true is that Mr Nkunda's forces are the single most serious threat to stability in the DR Congo," Mr Guehenno told Reuters news agency.
The dissident army general who belonged to the Rwandan-backed RCD rebel group, claims the government is promoting ethnic hatred.
Gen Nkunda and his troops say they are protecting the Banyamulenge - ethnic Tutsis who live in DR Congo.
The UN Security Council called on armed groups to stop fighting and recruiting soldiers, in a public statement read by China¿s ambassador Wang Guangya.
Rebels, who include suspects accused of participating in Rwanda's 1994 genocide, operate freely in the east of DR Congo.