As many as 4,500 civilians may have fled their homes in the eastern Democratic Republic of Congo following last week's launch of a military offensive against Rwandan rebel force, the United Nations said on Friday.

About 2,500 Congolese are reported to have been displaced in the Uvira area of South Kivu, the UN Office for the Coordination of Humanitarian Affairs (OCHA) said on the basis of information received from aid agencies.

“An additional 2,000 people may have also fled their villages as preventive measure,” OCHA added in response to The EastAfrican query.

“These figures are preliminary estimates as the area is volatile and aid agencies have not yet been able to carry out thorough assessments.”

The upheaval results from DRC army attacks launched on the Democratic Forces for the Liberation of Rwanda, an armed group known by its French acronym of FDLR.

The UN peacekeeping mission in the DRC noted that was not supporting the offensive and “is therefore not in a position to comment on the details of the operations.”

OCHA, however, said that “the humanitarian community remains extremely concerned about the protection of civilians due to the security vacuum in areas where armed groups are retreating, and due to difficulties in distinguishing non-combatants from combatants.”

About 70 per cent of the Congolese known to have fled their homes have found refuge in schools and churches in neighbouring villages, according to humanitarian organisations in the DRC. Others are said to be staying with host families.

The DRC armed forces chose to conduct a unilateral campaign against the FDLR after the UN refused to take part in the operation because it is being led by two Congolese generals described by the UN as having previously committed grave human rights violations.

But the UN peacekeeping force in the DRC, known as Monusco, says it is continuing to carry out its own mandate.

Monusco is encouraging voluntary disarmament by FDLR fighters, while monitoring human rights violations and facilitating the provision of humanitarian assistance to populations in need, according to a statement provided by the UN.

Monusco says it is also supporting military operations against other rebel forces, including the Allied Democratic Forces, which seeks to overthrow the government of Uganda.

The FDLR has been operating in eastern Congo for two decades following the 1994 genocide in Rwanda. Some of the group's leaders were involved in that mass killing, the UN says.

The mainly Rwandan Hutu rebels were given an ultimatum to surrender by the start of 2015 or face a military onslaught. Only a few fighters complied.

A Monusco combat brigade was initially poised to attack the FDLR in concert with the DRC army. But the UN declared last month that it would not play a supporting military role unless the two generals were removed from command. The DRC government responded by saying it would undertake its own campaign against the FDLR.

READ: DR Congo rejects UN ultimatum to sack tainted generals