Syrian government forces and their allies again laid siege to rebel-held eastern Aleppo on Sunday, while Turkish-backed fighters drove Islamic State from all the areas along its border, in two significant but separate developments in the multi-sided conflict.
The fighting - two potential turning points in the conflict if the gains can be sustained - complicated efforts by the United States and Russia to reach a ceasefire deal for Syria, whose civil war is in its sixth year.
Talks by the Cold War foes on a ceasefire were set to continue on Monday, but "we're not there yet," U.S. President Barack Obama told reporters at the G20 summit in the Chinese city of Hangzhou.
Syrian President Bashar al-Assad wants to fully recapture divided Aleppo, Syria's largest city before the war. Gains made by Damascus have relied heavily on Russian air support since September last year.