At least 55 people have been killed over the past 24 hours in the Syrian province of Aleppo as Russian air strikes resumed over the countryside, sources told Al Jazeera.

The deaths from raids in Aleppo’s Bustan al-Qasr and Fardos neighbourhoods, as well as Ar-Rasheeqa city, were the results of the heaviest Russian bombardment in days on the city’s rebel-held sector. Dozens were also wounded.

The Syrian Observatory for Human Rights, a Britain-based monitor, reported a lull in fighting on Wednesday.

“Silence is taking over Aleppo city, so far no gunshots or airstrikes have been heard, since the airstrike[s],” the monitor said.

Heightened tensions on the ground came amid efforts from the international community to halt the bloodshed in Aleppo.

Al Jazeera has seen a letter signed by at least 62 countries including Saudi and Qatar, but excluding Egypt and Iraq, calling on the UN Security Council to prevent further deaths from a “calculated campaign”.

The letter warns that the war in Syria is unlikely to be resolved by armies. It called on all parties to adopt political processes for a political transition based on recommendations agreed upon at Geneva conventions and by the Security Council.

“The fighting, the bombardment and the siege have worsened conditions inside Aleppo,” said Al Jazeera’s Zeina Khodr, reporting from the Turkish border with Syria.

“The United Nations is warning that drinking water remains limited, medical supplies are urgently needed and the distribution food rations are being split in half … aid agencies are appealing for access to treat the wounded,” Khodr added.

Read More: aljazeera