Ghadir Hajji rushed to a clinic on Sunday in hopes her five children would be among the first to get vaccinated against polio, which has re-emerged in war-ravaged Gaza.

"They absolutely have to be vaccinated," she told AFP as the family waited in line for a vaccine drive announced after health officials reported last month the first case of polio in the besieged territory in a quarter of a century.

"We received text messages from the ministry of health and we showed up right away."

She was joined by thousands of other Gazans whose fear of polio, which is highly contagious and potentially fatal, despite concerns for their personal security and rumours the vaccine would not be safe or effective.

Polio-virus is highly infectious and most often spread through sewage and contaminated water - an increasingly common problem in Gaza with much of the territory's infrastructure destroyed by Israel in its war against Hamas.

The disease mainly affects children under the age of five. It can cause deformities and paralysis, and is potentially fatal.

At one clinic alone in Deir el-Balah nearly 2,000 children were vaccinated on Sunday, said Louise Wateridge, a spokeswoman for the United Nations agency for Palestinian refugees, known as UNRWA.

The agency had mobile teams going from tent to tent, marking kids' thumbs with ink once they received their doses, Wateridge said.

The first doses were administered on Saturday to an unspecified number of children in the southern city of Khan Yunis, ahead of Sunday's large-scale rollout.

The campaign aims to vaccinate more than 640,000 children in the besieged Palestinian territory, devastated by almost 11 months of war.

On Thursday, the WHO said that Israel had agreed to a series of three-day "humanitarian pauses" in northern, southern and central areas to facilitate vaccinations.

Israeli Prime Minister Benjamin Netanyahu however, has insisted that these pauses were not amounting to any kind of ceasefire in overall fighting in Gaza. (AFP)