The Sudanese army and government-backed militias are committing acts of "inexplicable terror" against civilians, including children, in Darfur, the U.N.'s top humanitarian official said Saturday.

Spiraling violence in the conflict-wracked region of western Sudan is reaching its worst level since fighting erupted more than three years ago, Jan Egeland, the U.N. undersecretary-general for humanitarian affairs said.

"The government and its militias are conducting inexplicable terror against civilians," he said in an Associated Press interview just after returning from his final trip to the area before his term as U.N. humanitarian chief ends in December.

"The government is arming Arab militias more than ever before ... the angst is that we may be reverting to the same level of violence" as in 2003, he said.

More than 200,000 people have died and 2.5 million have been forced to flee their homes since fighting broke out after ethnic Africa tribes rebelled against the Arab-led government. Janjaweed, Arab militias supported by the government, are believed to be responsible for many of the atrocities.

U.N. officials and humanitarian workers have said that violence has increased since the government and one of several rebel groups signed a peace agreement in May.

"Civilians are being killed as we speak," Egeland said, warning that the crisis "still has the potential of becoming infinitely worse."

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At a separate news conference, Egeland said aid workers' ability to carry out their humanitarian mission was "crumbling" because of the violence. But he was hopeful that the Sudanese government's agreement for a mixed U.N. and African Union force would finally allow for "an effective international force" to be deployed in Darfur.

The agreement in principle reached Thursday between Sudanese envoys and the U.N. and AU for a mixed peacekeeping force raises hopes that a measure of stability could be returned to Darfur. That agreement comes after President Omar al-Bashir expressed opposition repeatedly in recent months to the deploying of a U.N. force in the area, even describing it as a neocolonialist plot.

But Sudan's Foreign Minister Lam Akol downplayed the deal, saying his government had not committed to such a mission.

"What we have agreed upon is that the force should remain African and it be assisted by the United Nations," Akol said on Saturday. "There is no way the main fighting force would be a mixed one."

Other officials have said a combined force would not pose a problem providing that its leadership and the bulk of its troops were African — a sign that Sudan's political leadership may be sending mixed messages in order to avoid the appearance of a policy shift in the face of Western pressure.

The current 7,000-strong AU force has been ineffective in preventing violence in the vast arid area of western Sudan that is roughly the size of Texas.

The continued attacks that harms civilians and hampers efforts to deliver humanitarian aid underline the need to upgrade the AU force, Egeland said.

While in Darfur the humanitarian official visited a government hospital in Geneina where survivors were being treated after an attack last week by government forces and janjaweed that killed 30 people.

"I saw a 2-year-old-girl who was shot in the neck at point blank by a janjaweed," Egeland said. "This is an act of terror." The baby's mother and several witnesses confirmed the attack was jointly conducted by the army and militias, he said.

He said a similar raid in Jebel Moon last month showed that the children were not accidental casualties. "It is not so-called collateral damage," Egeland said. "It is the intentional killing of children."

Another U.N. official, who spoke on condition of anonymity because of the sensitivity of the matter, said five children were killed by janjaweed fighters in North Darfur on Friday.

The Sudanese government denies backing or arming the janjaweed. It says uniformed fighters belong to regular forces and don't commit war crimes, while those clad in traditional garb are bandits it does not control. A government investigation said the Jebel Moon killing was committed by "renegade Arab bandits."

Egeland appeared to dismiss speculation that the international community had made a deal with Khartoum to accept U.N. peacekeepers in exchange for not seeking the prosecution of senior officials for crimes against humanity in Darfur.

"Those who continue to attack defenseless civilians will be judged," he said. "There will be a time of reckoning."