* UN chief suggests new force to combat Congo rebels
* Questions raised on command structure, ability of new force
By Michelle Nichols
UNITED NATIONS, March 5 (Reuters) - The U.N. Security Council hopes to approve by the end of March a special force to combat rebels in the Democratic Republic of Congo, but some members have concerns that need to be addressed first, Russia's U.N. envoy Vitaly Churkin said on Tuesday.
While Churkin did not divulge these concerns, some diplomats worry the creation of the intervention force within the existing peacekeeping operation, known as MONUSCO, could lead to two competing units. They want more detail on the new unit's command structure.
"We think it's very important that the intervention force is fully integrated into MONUSCO," said one senior council envoy, speaking on the condition of anonymity. "I don't see opposition" to the proposal, he said, "but we need a lot of clarification."
South Africa, Tanzania and Mozambique are the most likely candidates to supply the several thousand soldiers needed for the intervention force, but diplomats have questions about the ability of those troops to take on the rebel groups, including the M23, which have taken parts of eastern Congo.
"A lot of hard work is ahead of us in the next few weeks," Churkin told reporters after U.N. Secretary-General Ban Ki-moon briefed the 15-member council on his proposal to strengthen and define MONUSCO's mandate and create the intervention force.
"There are some issues to be sorted out ... Hopefully by the end of the month we will be able to adopt that mandate" resolution, said Churkin.
M23 began taking parts of eastern Congo early last year, accusing the government of failing to honor a 2009 peace deal. That deal ended a previous rebellion and led to the rebels' integration into the army, but they have since deserted.
"The intervention brigade will be tasked with containing the expansion of both Congolese and foreign armed groups, neutralizing these groups, and disarming them," Ban told the Security Council on Tuesday.
In practical terms, U.N. diplomats say, troops in the brigade will have more freedom to open fire without being required to wait until they are attacked first, a limitation that is standard for U.N. peacekeepers deployed around the world.
African leaders signed a U.N .-mediated deal late last month aimed at ending two decades of conflict in Congo's east and paving the way for the intervention force.
At least 70 people were killed and thousands more fled their homes after days of fighting between rebels and government forces in eastern Congo, aid agencies said on Tuesday.
The clashes that began last week underline the complex nature of the conflict in eastern Congo, where personal and local grievances fuel a wider battle between armed groups and the ill-disciplined army for control of land and the region's rich mineral deposits. (Editing by Philip Barbara)