The army captured the Sakhur, Haydariya and Sheikh Khodr neighbourhoods on Monday, while Kurdish forces took the Sheikh Fares district from rebels, the Syrian Observatory for Human Rights said.
Kurdish forces in Aleppo are not officially allied with the regime, but the opposition regards them as cooperating with the government in a bid to recapture the city.
"The rebels have lost control of all the neighbourhoods in the north of east Aleppo, and this is their worst defeat since they seized half the city in 2012," said Observatory director Rami Abdel Rahman.
Syrian state media reported the capture of Haydariya and Sakhur as it looped footage showing some of the thousands of civilians who have fled east Aleppo in recent days as loyalist troops have advanced.
The army renewed an operation to retake eastern Aleppo nearly two weeks ago, hoping to deal the opposition a potentially devastating blow. Syria's Al-Watan daily, which is close to the government, said the army was advancing quickly.
It said the next stage of the operation would be "to divide the remaining area into security districts that will be easily controlled and to capture them successively." The advance would then "push the gunmen to turn themselves (in)... or accept national reconciliation under the terms of the Syrian state."