Tens of thousands of people have been affected by the rebel raids
An offensive against Ugandan rebels in the Democratic Republic of Congo has been "catastrophic" for civilians, the UN humanitarian chief has said.
John Holmes was speaking after visiting Doruma, in the north-east, where at least 900 people have recently been killed by the Lord's Resistance Army.
The LRA has increased attacks since forces from Uganda, South Sudan and DR Congo began an offensive in December.
But Mr Holmes said the operation must continue against the rebels.
Countries from Uganda to the Central African Republic have suffered 20 years of terror inflicted by the LRA and tens of thousands of children have been abducted to be fighters and sex slaves.
The UN head of humanitarian affairs is due to end a four-day visit to DR Congo by meeting President Joseph Kabila and UN peacekeeping officials.
Last week, the UN force in DR Congo, known as Monuc, dismissed claims by humanitarian organisation Medecins Sans Frontieres that it was ignoring bloodshed in the north-east of DR Congo, near Sudan's border.
Mr Holmes admitted that Monuc had not done enough, but said that the force had limited resources in such a big country with different conflict areas.
It was difficult to deploy more troops to the area while Monuc was still waiting for 3,000 extra peacekeepers promised by the UN Security Council to deal with a separate conflict further south, he said.
Mr Holmes met some of the tens of thousands of people around Doruma who have fled their homes because of the LRA attacks.
One man told the BBC that the rebels had killed 15 members of his family.
"They crushed their heads with axes, they cut them with machetes and wooden bats," he said.
"Skulls were so crushed that we couldn't recognise anyone. They crushed everything, all bones.
The BBC's Thomas Fessy, travelling with the UN humanitarian affairs head, says the terrible truth is that all the people who fled the violence tell similar stories.
Mr Holmes said the displaced should return to their homes when they want to.
"We want to help people go home - that's the objective. We don't want people to stay in camps a day longer than they have to.
"But when they want to home then we can change the focus of our assistance to helping them here to helping them get back there."
Meanwhile, Ugandan army spokesman Captain Deo Akiiki said it was important for the operation against the rebels to continue, despite the upsurge in attacks.
"It is better to fight the LRA and finish them instead of leaving them to continue committing these atrocities," he told the BBC's Network Africa programme.
"We have already killed some, captured some…. And we're forcing some to surrender.
"It may not be today, it may not be tomorrow, but we shall get them like we have been getting them."
Capt Akiiki said his superiors would review a deadline - set for the end of this week - for Ugandan soldiers to leave DR Congo.
The LRA insists the International Criminal Court must drop warrants of arrest for its leader Joseph Kony and his top commanders before they can sign a peace deal, which has been on the table since last year.