UNITED NATIONS, Oct. 24 (Xinhua) -- An immediate ceasefire is needed in the Gaza Strip as the enclave faces the additional threat of polio spreading, if the final phase of a vaccination campaign continues to delay in the besieged North Gaza, a UN humanitarian official said on Thursday.

The third and final phase of the polio vaccination campaign, which was set to start on Wednesday in northern Gaza, had to be postponed due to the escalating violence, intense bombardment, mass displacement orders, and lack of assured humanitarian pauses.

"It is imperative to stop the polio outbreak in Gaza before more children are paralysed and the virus spreads," said Louise Wateridge, spokesperson for the UN agency for Palestine refugees (UNRWA). "The vaccination campaign must be facilitated in the north through the implementation of humanitarian pauses."

The current conditions, including ongoing attacks on civilian infrastructure, continue to jeopardise people's safety and movement in northern Gaza, making it impossible for families to safely bring their children for vaccination and health workers to operate, Wateridge said.

Since the beginning of the second round of the polio vaccination campaign on Oct. 14, 442,855 children under age 10 have been successfully vaccinated in central and south of Gaza, representing 94 percent of the target in these areas.

To interrupt the transmission, at least 90 percent of all children in every community and neighbourhood need to receive a second vaccination following the first round, including more than 119,000 children across northern Gaza.

The spokesperson said people in North Gaza are experiencing extreme suffering with "harrowing levels of death, injury and destruction."

More than 400,000 people remain trapped in the north where Israel has intensified its offensive against Hamas militants. For three weeks, there has been no food or aid reaching the north, and there are no markets or shops selling food. The military offensive has also cut off access to the essentials for survival, including water.

The Office for the Coordination of Humanitarian Affairs (OCHA) reported Thursday that families in Tel Al Zaatar, northeast of the Jabalya refugee camp, as well as west of the camp in Al Faluja, remain trapped and unable to move. Between 50,000 and 70,000 people are estimated to remain in Jabalya.

A request from the UN partners earlier this week to deliver 23,000 litres of fuel to North Gaza Governorate has been denied by Israeli authorities.

The Palestinian Civil Defense said that its operations have completely stopped in North Gaza Governorate, leaving the entire population there without humanitarian rescue services.

Since the Israeli ground offensive in the north began on Oct. 6, some 63,000 people have been newly displaced from North Gaza Governorate to Gaza City, OCHA estimated. ■