At least 20 children in Syria's largest city, Aleppo, are being seriously injured every day by government forces, Sky News has learned.
Although the Free Syrian army claims to control 60% of the city, the area is still coming under heavy bombardment from regime fighter jets.
Sky's special correspondent Alex Crawford has visited a hospital in an opposition controlled part of the city which medical staff say has been shelled six times.
She witnessed a boy being rushed in after shrapnel sliced through his lower chest, missing his lung by inches.
As he arrived at the hospital, he pleaded: "I am dying, I am dying, please can I have some water."
A father of another child also receiving treatment at the hospital said: "Bashar al Assad promised us reforms and all we are getting is killing. He is killing our children by the hundreds."
Doctors and nurses - all volunteers - are working in two rooms on the lower floor after jets bombed the upper levels.
Dr Abu Samir, who qualified just two years ago and is virtually running the hospital, said: "I feel pain inside in myself... More than 20 children a day come to the hospital."
Crawford said hospital staff were so overwhelmed that "dead children were being laid outside".
Earlier, Crawford witnessed fighter jets attacking targets near Marea, north of Aleppo, which included hospitals and a school on top of a house that was unoccupied at the time.
She said rebels remained "extremely bouyant and confident" that they can still defeat President Assad's loyalists.
"There is still shelling going on. The frontline which is just on the edge of Aleppo city - they are battling and trying to maintain control of an area just north of the city," she told Sky News later on Saturday.
"It's still very fragile there. They say there are seven regime tanks facing them, and certainly we came under fire from snipers as we were being shown part of the area which the Syrian army said they had control of."
She added: "Aleppo city, and control of it, is considered crucial really, and if Aleppo city falls to the Free Syrian Army then they very much will have the run of things and feel Damascus will be next.
"They are telling me they feel extremely buoyant and confident, and even without international help in the form of anti-aircraft weapons, they feel they are on course for victory and they are talking very bullishly of Damascus being next."
In Damascus, Syrian army forces launched arrest raids and clashed with rebels in the southwestern belt of the city in what activists described as a renewed bid to crush the insurgency in the capital "once and for all".
Shells from mountains overlooking the Syrian capital crashed into the suburb of Daraya as part of a regime offensive to regain control of the area. Activists said at least 15 people were killed, including three children and two women.
Activists also blamed a government warplane for bombing an apartment building in the eastern city of Mayadin, killing at least 21 people.
Meanwhile, new UN-Arab League envoy Lakhdar Brahimi has said he is "scared" at the size of the task of ending the Syria conflict.
The former Algerian foreign minister spoke as he started meetings with UN Secretary-General Ban Ki-moon, UN ambassadors and other top officials before replacing Kofi Annan on September 1.
"When you called me, I told you that I was honoured, flattered, humbled and scared. I am still in that frame of mind," Mr Brahimi told Mr Ban before their meeting at UN headquarters.
"I will definitely give this my very, very best. I know a few people in Syria and in the region," added Mr Brahimi, who as an Arab League envoy brokered the 1989 accord that ended Lebanon's civil war.
Mr Ban said that the new envoy faced a "crucial task" as the Syrian war worsens. The UN leader made a new plea for the divided UN Security Council to unite behind Mr Brahimi.
Mr Annan, a former UN chief, ended his six-month bid to bring peace to Syria, complaining about the lack of international support for his efforts to make Mr Assad implement an agreed peace plan.