The Kremlin said on Friday it wanted the Syrian government to restore constitutional order in the Aleppo region as soon as possible after an insurgent offensive there that captured territory for the first time in years.

Russia, a staunch ally of Syrian President Bashar al-Assad, intervened militarily on Assad's side against insurgents in 2015 in its biggest foray in the Middle East since the Soviet Union's collapse, and maintains an airbase and naval facility in Syria.

Rebels led by Islamist militant group Hayat Tahrir al-Sham launched an incursion on Wednesday into a dozen towns and villages in the northwestern province of Aleppo, which is controlled by Assad's forces.

It was the first such territorial advance since March 2020 when Russia and Turkey, which supports the rebels, agreed to a ceasefire that led to the halting of military action in Syria's last major rebel stronghold in the northwest.

Russian and Syrian warplanes bombed a rebel-held area near the border with Turkey on Thursday to try to push back the insurgents, Syrian army and rebel sources said.

Kremlin spokesman Dmitry Peskov said Moscow regarded the rebel attack as a violation of Syria's sovereignty and wanted the authorities to act fast to regain control.

"As for the situation around Aleppo, it is an attack on Syrian sovereignty and we are in favour of the Syrian authorities bringing order to the area and restoring constitutional order as soon as possible," said Peskov.

Asked about unconfirmed Russian Telegram reports that Assad had flown into Moscow for talks with Russian President Vladimir Putin, Peskov said he had "nothing to say" on the matter.