At least 26 people have been killed, including six children, in airstrikes from Monday, which have targeted rebel-held areas of the northern Syrian city of Aleppo, according to the UK-based monitoring group Syrian Observatory for Human Rights (SOHR), reports CNN.

Nine other people were wounded, some in critical condition, SOHR said. 

It wasn't clear who conducted the airstrikes, but the opposition and the US have blamed the Syrian regime and Russian warplanes for such attacks since a ceasefire broke down.

SOHR claimed rebel-held areas in the eastern part of the city had been struck by barrel bombs Tuesday, as fighting between regime and rebel forces continues throughout the city. Throughout the conflict the crude explosives have been the calling card of Syrian government forces.

Recent clashes and bombings have left Aleppo a near-ghost city.

The bombardment came after a bloody weekend which saw the deaths of 85 people and injuries to 300 others, and a day after the UN Security Council met in a special crisis meeting.

In that meeting, Secretary-General Ban Ki-moon and the US Ambassador to the UN, Samantha Power, separately described the Syrian regime's brutal offensive against areas of the besieged northern city of Aleppo as "barbaric."