The European Union said Saturday it was ready to increase assistance to the World Health Organisation (WHO) if an outbreak of polio is confirmed in war-ravaged Syria.

UN agencies are stepping up efforts to vaccinate children in Syria against a host of diseases and the WHO has received reports of 22 cases of acute flaccid paralysis (AFP), possibly caused by the poliovirus.

If so these would be the first cases in Syria since 1999.

"The situation is extremely worrying given the present security situation and the problems with access to those who will need to be vaccinated," said the EU's Humanitarian Affairs Commissioner Kristalina Georgieva.

"The European Union is prepared for such an eventuality," she said in a statement, noting that the 28-nation bloc has committed 13.5 million euros ($18.6 million) to the WHO since the beginning of the Syrian crisis and "we stand ready to do more if needed."

Overall, the EU has offered around two billion euros in aid since the conflict in Syria first erupted in March 2011.

The commissioner said she was in contact with the WHO epidemiology surveillance unit based in Amman, awaiting news on the cases.

"The EU hopes that we can nip this potential polio resurgence in the bud and spare the Syrian people from yet another source of suffering," she said.

The highly infectious disease affects mainly children under five and can cause paralysis in a matter of hours. Some cases can be fatal.