HAMILTON, Canada

The UN on Friday reiterated its serious alarm over escalating hostilities in Syria's northern city of Aleppo and warned that renewed fighting could further endanger civilians and disrupt humanitarian operations.

"I can tell you that we continue to be gravely alarmed by the hostilities in Aleppo," UN spokesperson Stephane Dujarric said at a news conference, adding that "despite ongoing efforts to try to calm the fighting, the dangers of renewed and further escalation and the impact on civilians are extremely concerning."

Emphasizing the need to respect "international humanitarian law to protect civilians and civilian infrastructure at all times," the UN spokesperson urged all sides to "avoid further escalation."

"We urge them to demonstrate restraint and take concrete steps to prevent any additional civilian casualties," Dujarric said, calling on "all parties to show genuine flexibility and good faith and to swiftly return to negotiations to ensure the full implementation of the March 10 agreement."

On the humanitarian situation, Dujarric said hostilities have restricted movement and delayed aid deliveries.

Despite the challenges, "we are coordinating with relevant groups so we can continue to deliver humanitarian aid," he said.

Fighting in Aleppo erupted on Tuesday when the YPG/SDF terror group launched attacks on residential areas, civilian facilities, and army positions, killing nine people and wounding 55 others, and displacing about 165,000 residents from Ashrafieh and Sheikh Maqsoud, according to the latest official figures.

In response, the Syrian army launched a “limited” military operation on Thursday, regaining control of Ashrafieh and Bani Zeid. By Friday evening, Sheikh Maqsoud remained the only neighborhood outside state control.