The situation in Syria is "catastrophic," the president of the International Committee of the Red Cross warned on Monday, urging "actions that translate into greater field access" for aid.

The United Nations Children's Fund (UNICEF) and World Health Organisation (WHO) meanwhile condemned the interruption of polio vaccinations in Raqa province, where rebels and jihadists are fighting.

In a statement after a three-day visit to Syria, ICRC president Peter Maurer said most of the country's population was being affected by the conflict.

"It is beyond dispute that the humanitarian situation in Syria is catastrophic," he said.

"I am deeply concerned by the fact that most of the population is directly or indirectly affected by spiralling violence and by constraints on humanitarian aid."

He warned that food and medical supplies were "dangerously short," especially in areas under siege.

Maurer said his visit had focused on urging officials to allow greater access for humanitarian aid.

"I welcome statements made by the various officials I met promising to allow more impartial aid, including medical aid, to everyone affected by the conflict," he said.

"However, with violence rising and needs growing, particularly in besieged areas, actions that translate into greater field access for the ICRC and the Syrian Arab Red Crescent must now follow."

The World Food Programme has said that half of Syria's population is food insecure, and nearly a third requires urgent assistance.