A top United Nations officials says deliberate interference, most notably by the Syrian government, continues to hinder the delivery of humanitarian aid to the over half million people trapped in besieged areas by the country's ongoing civil war.

Under-Secretary-General for Humanitarian Affairs Stephen O'Brien told the Security Council on Friday that 592,700 people are currently living under siege with the vast majority of them, some 452,700, besieged by Syrian government forces.

O'Brien, who spoke by video link, said that even when humanitarian aid deliveries had been approved, the Syrian government "has severely curtailed the U.N.'s ability to reach those in need."

Bashar Jaafari, Syria's U.N. Ambassador, disputed O'Brien's claims and accused Turkey of using the humanitarian convoys to deliver weapons to the government's enemies.