The situation in northern Democratic Republic of Congo where Lord's Resistance Army rebels operate is getting worse, a medical charity says.
Medecins Sans Frontieres told the BBC hundreds of thousands of people are fleeing renewed rebel attacks.
LRA leader Joseph Kony once operated from Uganda but his fighters now cover a vast area of central Africa.
Analysts says attempts this year by regional armed forces to halt the brutal campaign have so far failed.
The armies of Uganda, southern Sudan and DR Congo have been carrying out offensives against the rebels since Mr Kony refused to sign a peace deal late last year.
The rebels are infamous for carrying out mutilations and have kidnapped tens of thousands of children to be fighters and sex slaves.
Tens of thousands of people have also been made homeless during the LRA's two-decade insurgency.
'Living in fear'
MSF says roads in northern DR Congo are now so insecure that aircraft are being used to take supplies and staff to remote locations.
"The situation is really bad: the people are living in constant fear, they're fleeing," MSF's Operational Director Meine Nicolai told the BBC's Network Africa programme.
"The violence pops up in different areas and it's really expanding. It came to Congo in 2008 and now it's going more and more eastwards so the area is expanding and people live in constant fear."
Ms Nicolai said civilians were being targeted.
"People are kidnapped, raped, their houses are burned; they're fleeing, they leave everything and there's no way that they can return."
She said people desperately need food, water, medical care and psychological support.
Reports from the region suggest there are several groups of LRA fighters: some in DR Congo and another 1,300-strong force in the Central African Republic, led by one of Mr Kony's deputies.
Mr Kony himself is reportedly moving northwards, with reports suggesting Ugandan special forces are using helicopters to attack his group from Yambio in southern Sudan.
BBC Africa analyst Martin Plaut says there are also suggestions, yet to be confirmed, that Mr Kony's aim is to take his forces into the Sudanese region of South Darfur.
Last year Mr Kony, who is wanted by the International Criminal Court for war crimes and crimes against humanity,
failed to sign a peace deal with the Uganda government brokered by southern Sudan.