GENEVA: Some 400 civilians are in urgent need of medical evacuation from Syria's Eastern Ghouta region, including 29 who will die if they are not allowed to leave immediately, the United Nations warned Thursday.

"Around 400 men, women, children ... need to be evacuated now," Jan Egeland, head of the U.N.'s humanitarian taskforce for Syria, told reporters in Geneva, adding that 29 of them, including 18 children "will die if they are not evacuated."

As of now, "we have confirmation of seven patients dead because they were not evacuated, some of them children," he said.

The Eastern Ghouta region, near the capital Damascus, is one of the last strongholds of rebels fighting Syrian President Bashar al-Assad's regime.

Egeland said the region was now "the epicenter of suffering" in the war-ravaged country, with some 400,000 civilians stuck in a dozen besieged towns and villages.

The region, where a "de-escalation zone" deal was agreed by regime allies Iran and Russia and rebel backer Turkey in July, is now seeing increasingly dire conditions, he said.

"Since September, it has been completely sealed off," he said, pointing out that UN convoys are now the only lifeline to the area, and more often than not, those convoys are unable to get through.

"We cannot continue like that. If we get in only a fraction of what is needed, it would be a complete catastrophe," he said.

U.N. staff last week entered the area for a few hours and assessed that there are now "a growing number of acutely malnourished children," meaning they are "very close to dying," Egeland said.

He said many were babies whose mothers had been too malnourished themselves to breastfeed.

He pointed out that since May, efforts to carry out desperately needed medical evacuations from the area have largely failed, with only about a dozen patients evacuated to date.

This has created a situation where hundreds of civilians, most of them women and children, need to be evacuated.

They are currently languishing "in clinics, in basements, in makeshift hospitals inside the Eastern Ghouta besieged towns and villages," Egeland said.

"They range from acutely malnourished children ... to severely wounded civilians, children, women, men. We really cannot understand that they can't be evacuated," he added.

More than 330,000 people have been killed in Syria since the conflict began in March 2011 with anti-government protests, before spiraling into a complex, multi-front war that drew in international forces and extremists.