The World Health Organization (WHO) says polio vaccinations of children in central Gaza have "surpassed the target" in the first two days of its immunisation campaign.

Dr Rik Peeperkorn, the UN agency's representative in the Palestinian territories, said 161,030 children under the age of 10 were vaccinated on Sunday and Monday - above the projection of 156,500.

The difference was probably the result of an underestimate of the population crowded into the area, he explained.

Israel and Hamas agreed to a series of localised pauses in the fighting to allow health workers to administer vaccines after Gaza's first confirmed case of polio in 25 years left a 10-month-old partially paralysed last month.

The pauses are taking effect between 06:00 and 15:00 local time in three separate stages across central, southern and northern parts of Gaza.

The first three-day stage began in Deir al-Balah and Khan Younis governorates on Sunday. It will shift to the southern governorate of Rafah on Thursday and then move to North Gaza and Gaza City.

Dr Peeperkorn said the pauses had been "going well" until now.

But there were still "10 days to go at least" for the first round of the vaccination campaign, he said, while a second round to repeat the immunisations will start in four weeks.

He said some children were believed to be living outside the agreed zone for the pauses in the south and that negotiations were continuing in order to allow health workers to reach them.

The aim is to vaccinate a total of 640,000 children.

"We need to cover a minimum of 90% of those children to stop the transmission within Gaza and to avoid polio spread, international spread of polio to surrounding countries," Dr Peeperkorn said.

Poliovirus, most often spread through sewage and contaminated water, is highly infectious.

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

Humanitarian groups have blamed the re-emergence of polio in Gaza on disruption to child vaccination programmes as well as massive damage to water and sanitation systems caused by the war.

The mother of the partially paralysed baby, Abdulrahman Abu Judyan, told the BBC last week that her son was supposed to receive routine vaccinations on 7 October - the day Hamas attacked Israel and triggered Israel's military campaign in Gaza.

“I feel a lot of guilt that he didn’t get the vaccination. But I couldn’t give it to him because of our circumstances,” Niveen said.

She desperately hoped her son could be taken outside Gaza for treatment.

“He wants to live and walk like other children,” she said.