The top United Nations humanitarian official, making his first trip to Syria, said in Damascus on Monday that he was "absolutely horrified" at conditions there and "by the total disregard for civilian life by all parties."
While Stephen O'Brien did not single out specific combatant groups for blame, he was particularly critical of airstrikes that killed as many as 100 civilians Sunday in the central market area of Douma, a Damascus suburb.
The remark appeared to be aimed at Syrian President Bashar Assad, whose military is the only force based in Syria with access to air power.
Beyond the human toll, O'Brien said the civil war also has destroyed historic sites in Syria on a massive scale. He said that during his three-day trip he had visited the city of Homs, "where almost every home" in the Old City "had been completely destroyed."
O'Brien's visit was designed not only to call attention to the crisis in Syria, but also to put new pressure on U.N. members to close shortfalls in the delivery of humanitarian aid.
Contributions so far this year amount to less than a third of the funds needed to provide for victims, said O'Brien, who described the ongoing attacks on civilian areas as "appalling."
"We cannot scale up our operations to reach more people if we do not have adequate resources," said O'Brien, who took over the job from longtime U.N. humanitarian chief Valerie Amos in June .
More than half of Syria's 22 million people have either fled the country or been internally displaced from their homes in the still-expanding war, according to U.N. figures. O'Brien said that at least a quarter-million people had been killed, with more than a million injured.
He said armed groups, which he did not identify, had cut water supplies to at least 5 million people in Damascus, and 2 million in Aleppo.
State Department spokesman John Kirby condemned the Douma airstrikes, which he said "demonstrate the regime's disregard for human life."
Separately, the U.N. special envoy to Syria, Staffan de Mistura, said that "hitting crowded civilian markets, killing almost one hundred of its own citizens by a government is unacceptable in any circumstances." He repeated calls for a dialogue between the warring sides to forge a political settlement.
In New York, the U.N. Security Council on Monday issued a unanimous statement calling on all parties to the Syrian conflict to engage in "good faith" efforts to support efforts by de Mistura to begin a new round of negotiations toward a transition government. The document, adopted by consensus, included backing from Russia, which, along with Iran, has supported Assad's government.
The United States has been by far the largest donor of humanitarian aid to Syria, with combined food, refugee assistance, donations to international organizations and other aid totaling $4.1 billion since 2012, according to the U.S. Agency for International Development.
The humanitarian plight of Syrian civilians, regarded as the world's biggest refugee crisis, is frequently overshadowed beyond the region by the U.S.-led military campaign against the Islamic State.