A campaign to vaccinate a final 200,000 children in north Gaza against polio began although health and aid officials said the operation was complicated by access restrictions, evacuation orders and shortages of fuel, Reuters reports.

The campaign in north Gaza, the part of the territory hardest hit by Israel’s 11-month military offensive against Hamas, follows the vaccination of more than 446,000 Palestinian children in central and south Gaza earlier this month.

Medical staff had started administering vaccines in the north despite a dire need for fuel, among other challenges, said Dr Moussa Abed of the primary care unit in Gaza’s health ministry.

Vaccination centres are in areas that are militarily very active, difficult to reach and isolated if things go wrong, said Sam Rose, a deputy director of the UN agency for Palestinian refugees, UNRWA.

“There are some nerves, but we’ll have to make it work,” he told Reuters by text message.