Casualties mount in Aleppo bombardment

100 children die in week of fighting

BEIRUT, Lebanon — An array of groups allied with the Syrian government pressed an assault Friday on rebel-held eastern Aleppo as the World Health Organization said heavy bombardment of the area by Russia and Syria had killed 338 people in the past week, including more than 100 children.

With more of the city’s already limited hospitals destroyed in the latest offensive, Dr. Richard Brennan, the organization’s director of emergency response, told reporters that many of the 846 people wounded were expected to die for lack of treatment. That includes 261 children, he said.

There were competing claims about the success of the government’s offensive on Friday, with the government saying its fighters had captured more territory in northern parts of the city and penetrated the center of Aleppo, where they were clashing with the rebels.

Rebel commanders denied the reports, however, saying government forces had not made any progress since capturing the Handarat refugee camp north of the city on Thursday.

International monitoring groups have accused Russia and Syria of bombing civilian targets, like hospitals, schools and basic infrastructure, without regard to the safety of the civilian population of 250,000 in eastern Aleppo. On Friday, the rebels said the government bombed the main water plant that supplies the area.

After five years of civil war, the Syrian Army has been reduced to just a few effective and experienced units, analysts say, and is no longer capable of prosecuting a broad offensive on its own. That has created a void that is being filled by groups from outside the country: Shiite militias and mercenaries from Iraq and Afghanistan, fighters with the Lebanese militant group Hezbollah, and soldiers from Iran’s Islamic Revolutionary Guards Corps and its elite Quds Force.

Those militias have been backed by a Russian air campaign that has “hit civilian areas and increasingly used indiscriminate weapons, including cluster and incendiary munitions,” Britain’s special representative to Syria, Gareth Bayley, said in a statement Friday. Others have accused Russia of using bunker buster bombs meant for military targets, while the American ambassador to the United Nations, Samantha Power, has called the attacks “barbarism.”

Russia’s foreign minister, Sergey V. Lavrov, told the BBC on Friday that Russian forces were not using “any munition which is prohibited by the United Nations.”

Russia has also accused the United States, under the guise of backing the opposition in the civil war, of abetting terrorism and helping militant groups like the Nusra Front, an affiliate of al-Qaida, and the Islamic State.

Mr. Lavrov said Washington had “pledged solemnly to take as a priority an obligation to separate the opposition from Nusra,” but that the United States had shown that it was “not able or not willing to do this.”