The UN Security Council has unanimously approved the first-ever "offensive" UN peacekeeping brigade to battle rebels groups in the Democratic Republic of Congo.

The force of more than 2,500 troops will operate under orders to "neutralise" and "disarm" armed groups in the resource-rich east of the huge country, according to the council's resolution on Thursday.

The intervention brigade is unprecedented in UN peacekeeping because of its offensive mandate.

But the resolution states clearly that it would be established for one year "on an exceptional basis and without creating a precedent" to the principles of UN peacekeeping.

Surveillance drones will be used to monitor the DR Congo's borders with neighbours accused of backing the rebels will be operating by July, according to UN officials.

The resolution, sponsored by France, the US and Togo, would give the brigade a mandate to operate "in a robust, highly mobile and versatile manner" to ensure that armed groups cannot seriously threaten government authority or the security of civilians.

UN peacekeepers were unable to protect civilians from M23 rebels, whose movement began in April 2012 when hundreds of troops defected from the Congolese armed forces.

The resolution strongly condemns the continued presence of the M23 in the immediate vicinity of Goma, the capital of North Kivu province, and its attempts to establish "an illegitimate parallel administration in North Kivu".

It demands that the M23 and other armed groups, including those seeking the "liberation" of Rwanda and Uganda, immediately halt all violence and "permanently disband and lay down their arms".

It also strongly condemns their continuing human rights abuses including summary executions, sexual and gender-based violence and large-scale recruitment and use of children.

Border violence

Besides disbanding armed groups, the resolution says the intervention brigade will monitor an arms embargo along with a panel of UN experts and observe and report on the flows of military personnel, weapons and equipment across the border of eastern Congo including by "surveillance capabilities provided by unmanned aerial systems."

The brigade will be part of the UN peacekeeping mission in Congo, known as MONUSCO, within its troop ceiling of 19,815.

The UN currently has more than 17,700 UN peacekeepers and more than 1,400 international police in Congo.

The resolution extends MONUSCO's mandate until March 31, 2014. The "intervention brigade" headquarters will be in the key eastern city of Goma and UN officials say it will probably include between 2,000 and 3,000 troops.

The brigade and drones are part of a new UN campaign to end conflict in DR Congo's border regions with Rwanda and Uganda.

Eleven African nations signed a UN-brokered accord last month pledging not to interfere in the affairs of their neighbours. Rwanda, a temporary African member of the Security Council, joined the other 14 members in voting for the resolution.

Congo has been engulfed in fighting since the 1994 Rwanda genocide, in which at least 500,000 Tutsis and moderate Hutus were slaughtered by Hutu militants before a Tutsi-led rebel army took power in Rwanda.

More than 1 million Rwandan Hutus fled across the border into Congo, and Rwanda has invaded Congo several times to take action against Hutu militias there.