iStock/Thinkstock(LONDON) — East Aleppo saw what witnesses describe as an unprecedented and relentless offensive as United Nations diplomats demanded a halt to the violence Sunday.

On Monday morning airstrikes continued to hit the rebel-held part of Aleppo, say locals.

“Six have died at the hospital so far since airstrikes started to hit this morning,” Abu Rajab, a nurse at an Aleppo hospital, told ABC News.

Sunday’s airstrikes were heavier than anything he had seen or heard since the Syrian war started over five years ago, he said.

“It felt like the ground was shaking under you, like an earthquake,” he said of the strikes. “The explosions sounded loud and strange like nothing we’ve heard before in five years of war. It was a bloody day. No words can describe what happened yesterday.”

He said the hospital received around 180 injured people from Sunday’s attacks, but had to refer some of them to other clinics because they didn’t have the capacity to treat all of them. Around 40 percent of the wounded were children and 20 percent women, he said. The intensive care unit was so filled up with patients that one surgeon had to conduct an operation on the ground.

Since midnight Saturday, at least 27 people were killed by strikes from warplanes and government helicopters, the Syrian Observatory for Human Rights said Sunday.

At least 70 people have been killed in three days of airstrikes on east Aleppo from Friday to Sunday night, activists in Syria told ABC News.

The United Nations said the recent attacks on Aleppo could amount to war crimes.

“Repeated airstrikes and the use of bunker-busting and incendiary bombs in densely populated areas could well prove to be war crimes,” David Swanson, a spokesman for the U.N. Office for the Coordination of Humanitarian Affairs, told ABC News.

The U.N. has 40 trucks with aid ready to enter eastern Aleppo. The aid has been sitting by the Turkish border for about two weeks and is still waiting by the border in Syria customs area. Once the U.N. gets the green light, the first convoy carrying a month’s worth of wheat flour for more than 150,000 people will be sent to Aleppo, according to the U.N.’s Office for the Coordination of Humanitarian Affairs. The shipment will be followed up by a delivery of enough food rations to feed 35,000 people for a month.

The distance from the Turkish border to east Aleppo is only some 40 miles, but the journey could take about four to five hours.

While up to 275,000 people in eastern Aleppo are still waiting for the aid they need, humanitarian assistance entered the four besieged Syrian towns of Madaya, Foah, Zabadani and Kefraya Sunday.

On Wednesday evening, one out of two water pumping stations in east Aleppo, was destroyed by airstrikes. In retaliation, rebels turned off the second water pumping station that mainly serves the government-held western part of the city. That means that close to 2 million people in Aleppo are currently living without running water.

At an emergency meeting Sunday, Western U.N. diplomats condemned the recent escalating violence in Aleppo and blamed Russia and the Syrian government. Samantha Powers, U.S. Ambassador to the U.N., accused Russia of committing barbarism under the guise of “counter-terrorism.”

“Instead of pursuing peace Russia and Assad make war. Instead of helping get life-saving aid to civilians, Russia and Assad are bombing humanitarian convoys, hospitals and first responders who are trying desperately to keep people alive,” Powers told members of the Security Council Sunday.

“It seems the only items that make it into eastern Aleppo these days are barrel bombs and incendiaries that witnesses report seen dropped by Assad’s forces and Russian forces. Russia of course has long had the power to stop this suffering. Even now, we will continue to look for any way possible to restore the cessation of hostilities.”

Powers walked out of the emergency session along with the French and U.K. ambassadors to the U.N. in protest when Syria’s ambassador was called to speak.

The U.S., the U.K. and France had requested the emergency meeting after the Syrian military on Thursday announced a new offensive on east Aleppo.

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