Nightly News | July 30, 2012
>>> syria's top diplomat here in london defected today criticizing the assad regime on his way out for their crackdown on the rebels that has killed upwards of 20,000 people so far. in syria the fighting goes on, a lot of it over control of the biggest city there, aleppo , the city the size of chicago, illinois, where the rebels have made their stand. we have been able to get a report out again tonight from our chief foreign correspondent richard engel , who is covering the fighting from inside syria .
>> reporter: the government assault on aleppo is strangling the city. u.n. officials say some 200,000 people have fled aleppo in the last two days alone. syrian troops seemed determined to drive the rebels out of this city along with many of its 3 million residents. the rebels are trying to fight back. but the rebels aren't completely defenseless. they filled gas canisters with shrapnel to make their bombs more deadly then spread fertilizer on the floor and add aluminum powder. now it's a dangerous mix. as they fill the canisters with the explosive, tiny, combustible particles float in the air. one spark and it'll all go up. these are crude bombs but as rebel internet videos show they're powerful. yet it's civilians suffering the most here. we've seen government troops shelling civilian areas indiscriminately. this doctor is the only surgeon for 70,000 people. he's trying to stay neutral.
>> we told them to fight only the army not the people. i told the government you must fight the free army only.
>> reporter: the dr. treats dozens of injured a day and bloody gauze on his floor and his medicine cabinet is nearly empty. this mother came today to find her son shot in the head by a government sniper. answer me, answer me, my life, s she wails, but he never did. one more of the some 20,000 killed in a war that appears to be growing more deadly by the day. richard engel , nbc news, northern syria .