The UN has accused armed groups in Syria of blocking the delivery of aid to the besieged city of Aleppo for “political gain” - including rebel factions inside Aleppo itself who say they will reject aid that comes through regime territory.

Two days after the Syria ceasefire agreement went into effect, bombs have stopped falling on the rebel-held eastern half of Aleppo but the 275,000 people living there are still desperately short of food and medical supplies.

A convoy of 20 UN trucks carrying enough aid for 40,000 people is languishing at the Turkish border as diplomats try to secure agreement from both rebels and regime forces to allow the vehicles through.

“Some parties to the conflict are trying to use this for political gain,” said David Swanson, a UN spokesman. “The challenge for us is ensuring that all parties to the conflict are on the same page. If one element of the chain is not there we cannot proceed.”

The UN would not say if the hold was up was being caused by the Assad regime or its rebel opponents but at least part of the problem appeared to be inside east Aleppo itself.

Activists there said they intended to reject the UN aid in protest at the ceasefire agreement which was brokered between the US and Russia without input from the Syrian opposition.