UNITED NATIONS, Feb. 14 (Xinhua) -- The UN special envoy for Syria on Wednesday stressed the need for the immediate de-escalation of violence in Syria.

"This is as violent and worrying and dangerous a moment as any that I have seen in my time as special envoy," Staffan de Mistura told the Security Council.

"I strongly reiterate the appeal of the (UN) secretary-general to all concerned in Syria and the region and beyond to de-escalate immediately and unconditionally, and urge all stakeholders ... to use their influence to help reduce violence," Staffan de Mistura said.

There has been a gradual return to back-and-forth competition over territory in Idlib and Hama provinces, and heavy and sustained airstrikes across the northwest and in besieged eastern Ghouta, said de Mistura.

Civilians have been killed on a horrific scale and strikes have continued to hit hospitals, schools and markets. Reports suggest that more than 1,000 civilians lost their lives in the first week of February alone, he said.

There have been several allegations of chemical weapons attacks in Ghouta and Idlib, and in the Afrin district on the border with Turkey, he said.

Although those allegations cannot be verified as there is no independent investigation, they are extremely worrisome, said de Mistura.

At least 320,000 people have been displaced due to fighting in Idlib in just two months, an area that is already hosting over 1.2 million internally displaced people, he said.