US Secretary of State John Kerry said Thursday he discussed Ukraine and "all aspects" of Aleppo including renewed bombing in the Syrian city this week in a meeting with Russia's Foreign Minister Sergei Lavrov.

Speaking to reporters after their one-on-one talk during the Asia Pacific Economic Cooperation summit in Peru, Lavrov denied that Russia's military was carrying out airstrikes in rebel-held Aleppo this week.

"Our air force and the Syrian airforce only work in the provinces of Idlib and Homs to prevent the ISIL who might be leaving Mosul from getting to Syria," Lavrov said, referring to Islamic State militants in Iraq.

Air strikes and shelling in rebel-held Aleppo has killed dozens this week, according to a monitoring group. The bombardment restarted Tuesday after a four-week pause, part of a wider military escalation by the Syrian government and its allies, including Russia, against insurgents.

Lavrov did not comment when asked about the future of the Iran nuclear agreement that Russia helped broker once Donald Trump, who has vowed to dismantle it, becomes president of the United States.