The United Nations on Tuesday said that close to 16,000 people have fled Syria recently, after government forces backed by Russia launched a massive offensive to recapture the city of Aleppo. The international body said that more civilians are likely to follow suit. UN humanitarian chief Stephen O’Brien described the situation as “alarming and chilling”.

He issued a statement in which he said that over 16,000 people have been “displaced, many into uncertain and precarious situations”. However, the estimated figure does not take into count those who have fled to rebel-held territory, reported AFP.

O’Brien told BBC that shelling of civilian areas in government-controlled western Aleppo by rebels has displaced more than 20,000 people in the past few weeks. The civilians have either fled to the rebel-held territory or have crossed over to government-controlled western Aleppo or Kurdish districts.

Russia has claimed the strikes on Aleppo “liberated” people. Russian defence ministry spokesperson Major General Igor Konashenkov told reporters, “Half of the territory in parts of eastern Aleppo occupied by militants in recent years has been completely freed... Our Western counterparts are showing surprising blindness when it is time to assess the real situation in Aleppo.”

Troops backed by Syrian President Bashar al-Assad have recaptured more than a third of the rebel-held eastern Aleppo. On Monday, the Syrian Observatory for Human Rights had said that government forces seized Sakhour district from rebels in the region. “It is the biggest defeat for the opposition in Aleppo since 2012,” the observatory’s director Rami Abdulrahman had said. Besides, Assad-backed troops have also recaptured rebel strongholds like Masaken Hanano and Jabal Badra districts.

The observatory had also said that more than 250 civilians have lost their lives in the exchange of fire.

Fighting between forces loyal to Syrian president Bashar al-Assad and rebel groups intensified after a ceasefire deal broke down in September when an aid convoy was bombed in Aleppo. More than 3,00,000 people have died in the six-year-long civil war and nearly half the country’s population has been forced to flee since it began. The civil war in the West Asian country began in 2011 following massive protests against the Assad regime. The Syrian government has been accused of committing atrocities against civilians such as dropping barrel bombs in populated areas as well as using chemical weapons.