GENEVA: Up to 20,000 people have fled a Syrian regime’s offensive in opposition-held eastern Aleppo in the last 48 hours, the International Committee of the Red Cross said Tuesday.

A spokeswoman for the Geneva-based ICRC, Krista Armstrong, told AFP that the 20,000 figure was an estimate and that the situation remained fluid, stressing that “people are fleeing in different directions,” desperately seeking refuge from the brutal fighting. Terrified civilians have fled empty-handed into remaining opposition-held territory, or crossed into regime-seized western Aleppo or Kurdish districts.

The Syrian government offensive to recapture rebel-held parts of Aleppo has sparked international alarm.

France called for an immediate UN Security Council session on the fighting, which has seen the army capture a third of opposition-controlled east Aleppo in recent days.

The UN humanitarian chief Stephen O’Brien had earlier put the number of displaced from eastern Aleppo at 16,000, describing the situation as “chilling.”

“The intensity of attacks on eastern Aleppo neighborhoods over the past few days has forced thousands of civilians to flee to other parts of the city,” O’Brien said in a statement.

“It is likely that thousands more will have no choice but to flee should fighting continue to spread and intensify over the coming days,” he warned.

His comments came as the regime forces advanced deep inside the longtime opposition stronghold of east Aleppo, taking several neighborhoods in an onslaught to recapture the entire city.

Jens Laerke, spokesman for the UN humanitarian agency, told reporters in Geneva Tuesday that a full 10,000 of those fleeing the intense battles in eastern Aleppo have gone to districts held by the regime in the west of the city.

As many as 6,000 others had headed to the Kurdish-held Sheikh Maqsud neighborhood, he said. O’Brien voiced concern over the “deeply alarming and chilling situation unfolding” across all of Aleppo.

“The parties to the conflict in Syria have shown time and again that they are willing to take any action to secure military advantage even if it means killing, maiming or starving civilians into submission in the process,” he said.

The situation in eastern Aleppo is dire, with intensified ground fighting and indiscriminate aerial bombardment reportedly killing and injuring many civilians, he said.

“There are no functioning hospitals left, and official food stocks are practically finished.”

At the same time, indiscriminate shelling on regime-controlled western Aleppo has killed and injured civilians and has displaced more than 20,000 people in recent weeks, O’Brien said.

The World Food Programme’s last warehoused stocks in eastern Aleppo, where some 250,000 civilians have been besieged for months, were distributed on Nov. 13, spokeswoman Bettina Luescher told reporters. The lack of food is “really dire,” she said, warning that the people stuck in the east were in a “slow-motion descent into hell.”

The UN human rights office meanwhile voiced alarm at the dangers facing those attempting to flee the fighting. “Adding to the dangers associated with attempting to flee across an active front-line, we have received reports that opposition groups are preventing civilians from leaving areas under their control,” spokeswoman Ravina Shamdasani said.

She also voiced concern that civilians believed to have links to armed opposition groups could be detained once they reach government or Kurdish-controlled areas. She warned that the use of the “terrorist” label “has in the past been used to punish peaceful activists and family members.”