The Syrian government has refused a UN request for humanitarian aid access to rebel-held eastern Aleppo, AFP reports, as the UN warns that the area could soon be besieged.

"The horrific fighting and bombardment in recent days, especially in and around Aleppo, is creating new areas with endless suffering and no access for humanitarians," said Jan Egeland, who heads an international humanitarian taskforce for the war-ravaged country.

Speaking to reporters after a meeting of the taskforce created in February by the 17-nation International Syria Support Group (ISSG), he said the situation in Aleppo needed to change immediately.

"If not, eastern Aleppo may even become a besieged area," he warned.