Forces loyal to Bashar al Assad took the Sakhour, Haydariya and Sheikh Khodr neighbourhoods on Monday and Kurdish forces captured 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 rebels regard them as co-operating with the government in a bid to recapture the city.
Observatory director Rami Abdul Rahman, who is based in the UK, said: “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.”
Analysts said the taking of the Sakhour district could cut the area held by the opposition in two and it is just a matter of time before all of eastern Aleppo is all under government control.
Syrian state media also reported that the Haydariya and Sakhour districts had been taken as it showed looped footage of some of the thousands of civilians who have fled the city.
Government forces have been fighting a renewed campaign in the last month to take the rebel-held east of Aleppo.
Hundreds of people are believed to have been killed in attacks that have seen every hospital in the east hit since July.
Thousands of people have fled the fighting, which has seen four districts seized from rebels in the last 24 hours with another six taken in the last few days, according to Mr Abdul Rahman.
Some have gone to government or Kurdish-controlled areas and others have headed south to the few remaining rebel-held districts.
At least 120 British MPs have backed a petition calling for the UK Government to carry out aid drops over eastern Aleppo.
Among those demanding the dispatch of “life-saving aid” to the war-torn city are senior Conservatives Andrew Mitchell, Michael Gove, Nicholas Soames and Alistair Burt.
Meanwhile, a Syrian girl who has been sharing the horrors of living in Aleppo on social media has revealed her home was destroyed and she narrowly escaped death in the fighting.
Bana Alabed, whose posts have been retweeted by author JK Rowling, described how she had nearly died after her neighbourhood, which is unknown, came under “heavy bombardment”.