The World Health Organization is “extremely worried” about the possibility of an outbreak of the highly infectious polio virus in Gaza after traces were found in wastewater.

Axar.az reports that Dr Ayadil Saparbekov, head of the WHO’s team in the Palestinian territories, told reporters a risk assessment was being implemented and that in the meantime health workers were providing protection advice to Gaza's 2.3 million population.

But, he added, it would be “very difficult” for people to follow it, given the breakdown of water and sanitation services.

Traces of polio - which is spread through faecal matter - were found in sewage samples collected from two sites in Gaza a month ago, indicating it may be circulating.

No associated paralytic cases have been recorded so far. But the Israeli military said on Sunday that it had begun vaccinating its soldiers.

The WHO and the UN children's agency (Unicef) believe a mass vaccination campaign may be needed in Gaza.

However, the repeated delays for aid workers and humanitarian supplies getting into Gaza, and huge security risks moving around the territory, mean an effective campaign will be very challenging.