Troops in the Democratic Republic of Congo (DRC) are preparing to launch an offensive against rebel fighters in the country's east with possibly limited logistical support from the UN.

Al Jazeera's Malcolm Webb, reporting from Goma, said on Saturday that the operation against the Democratic Forces for the Liberation of Rwanda (FDLR) was originally meant to be a joint effort between the UN and the Congolese army, but that was no longer the case.

"It was announced a couple of days ago that this is no longer a joint effort, but rather it will be carried out by the Congolese Army with UN logistical support," he said.

Who are the FDLR? [Al Jazeera]

Originally, a UN security brigade was expected to be involved directly in the mission against the rebel fighters, but Webb said the Congolese Army seemed to only want support from the UN's helicopter gunships.

"According to its own rules, the UN can't be involved in fighting unless it is also involved in commanding the operation," he added.

"Western countries will now be wondering why the operation hasn't begun, and why the UN's fighting role has been dropped."

FDLR is the largest rebel group in the eastern DRC with about 1,400 fighters. Some of them are accused of taking part in the 1994 genocide in Rwanda, before crossing over the border into the DRC.

The FDLR is more mobile than the M23 rebels, another armed group operating in the country, and would be able to split into factions and blend in with villagers, making it more difficult to single them out, our correspondent said.

AU talks

The efforts to push the FDLR out of the DRC are also on the agenda at the African Union summit in the Ethiopian capital.

Al Jazeera's Catherine Soi, reporting from Addis Ababa said the leaders were aware of the need for the offensive, but had concerns about the humanitarian fallout.

"The leaders here certainly understand the need to bring stability to the DRC and the need for this offensive to rid the DRC of its rebels," she said. "There are many concerns, however, about possible civilian casualties and humanitarian concerns."

The charity Oxfam is one of many human rights groups to express concerns about the operation and how effectively the contingency plans will protect the country's citizens.

"During 2009 there were similar operations and about 1000 FDLR fighters were disarmed," Louise Williams from Oxfam told Al Jazeera.

"For every one fighter disarmed, we know one civilian was killed, seven women or girls were raped, six houses were burnt and 900 people displaced.

"What we're doing is saying remember what happened in 2009 and how serious the implications were."

On Saturday, the African Union also agreed to send 7,500 troops from five West African nations to fight Boko Haram in Nigeria.

The move came after the council urged heads of state to endorse the deployment of African troops to fight the armed group, said the head of the African Union's Peace and Security Council, Samil Chergui.