The drive by 5,400 troops from the Democratic Republic of Congo army is also expected to bring instability and human rights abuses in the eastern Congo, which is plagued by war, The Guardian reported.
The offensive -- which began in the province of South Kivu, which borders Rwanda and Burundi, and is moving this month into North Kivu, bordering Uganda -- has stretched into areas north and west of the two provinces.
The offensive targets the Rwandan Hutu rebel group Democratic Forces for the Liberation of Rwanda, the local armed groups mai-mai and Joseph Kony's Lord's Resistance Army, sources told The Guardian.
The newspaper reports there are growing concerns civilians could be affected by the offensive, dubbed Operation Perfect Peace, and it will end the calm that came in the past year when the DRC army withdrew many regiments for reorganization and retraining.
"The international community is struggling to keep a lid on eastern Congo," said Anais Lafite, Oxfam's provincial coordinator for South Kivu, based in Bukavu. "They are trying to maintain the status quo for fear that worse might follow. … About 100,000 people have already been displaced since last October. It's estimated the current operation could displace a further 100,000."
A joint U.N.-Congolese army offensive targeting the Democratic Forces for the Liberation of Rwanda in 2009 was blamed for contributing to more than 1,000 civilian deaths, mass rapes of more than 4,500 women and forced displacement of more than 800,000 people, The Guardian said.
The Congolese army is notorious for human-rights abuses.