UN aid chief Mark Lowcock described the "horrific" conditions in northwest Syria to Anadolu Agency in an interview Friday.

The region has been witnessing a "terrible situation" for the past few months, he said, with an estimated 3 million Syrians cramped by the offensive by the forces loyal to Bashar al-Assad.

"I haven't seen anything really as horrific as what's happening now in northwestern Syria. And people are out in the cold in the mud, babies are dying and every day we're getting reports of this violence," said Lowcock.

Syrians who fled Eastern Ghouta are displaced in Idlib province and are still under the threat of bombs without shelter and education, he said, describing a scene of a brutal campaign by the Syrian regime and Russia.

Idlib, near Turkey's southern border, falls within a de-escalation zone laid out in a deal between Turkey and Russia in late 2018.

The Syrian regime and its allies, however, have consistently broken the terms of the cease-fire, launching frequent attacks inside the territory where acts of aggression are expressly prohibited.

The aid chief said people are congested in "very cramped conditions" in northwest Syria without protection. "There's nowhere safe anymore in Idlib."

A humanitarian worker with a health facility working to help Syrians was killed in a bombing Thursday, he said. "Unless this [violence] stops, unless these people [are] protected, I am afraid, we will see the biggest humanitarian horror story the world has seen in the 21st century."

The Syrian population in Idlib is "caught up in a problem" and they are trying to escape from it, said the aid chief.