UNITED NATIONS, United States - The United Nations launched an appeal for $397 million on Tuesday to help earthquake victims in Syria, where the disaster has killed thousands of people and left millions more in desperate need of aid.

Secretary-General Antonio Guterres, announcing the appeal at the UN headquarters in New York, said the funds would bring "life-saving relief" for nearly five million Syrians and would cover a period of three months.

He added that the world body was in the "final stages" of a similar appeal for Turkey.

"One week after the devastating earthquakes, millions of people across the region are struggling for survival, homeless and in freezing temperatures. We are doing all we can to change this. But much more is needed," Guterres pleaded.

He called on member states to "fully fund this effort without delay and help the millions of children, women and men whose lives have been upended by this generational disaster."

Guterres also urged that aid workers be allowed to operate freely in Syria, already racked by 12 years of civil war.

Activists and emergency teams in Syria's northwest have decried the slow UN response to the quake in rebel-held areas, contrasting it with the planeloads of humanitarian aid that have been delivered to government-controlled airports.

Before the earthquake struck, almost all of the crucial humanitarian aid for the more than four million people living in rebel-controlled areas of northwest Syria was being delivered through just one crossing.

Guterres announced on Monday that Syrian President Bashar al-Assad has agreed to open two more border crossings from Turkey to northwest Syria to allow in aid.

"The human suffering from this epic natural disaster should not be made even worse by manmade obstacles -- access, funding, supplies," said the UN chief.

"Aid must get through from all sides, to all sides, through all routes -- without any restrictions."

The United Nations has already provided $50 million through its central emergency response fund.

AFP