Israel's military and Palestinian militant group Hamas have agreed to three separate, zoned three-day pauses in fighting in Gaza to allow for the first round of vaccination of 640,000 children against polio, a senior World Health Organization official said on Thursday.

The vaccination campaign is due to start on Sunday, with the pauses scheduled to take place between 6 a.m. and 3 p.m., said Rik Peeperkorn, the WHO's senior official for the Palestinian territories.

He said the campaign would start in central Gaza with three consecutive daily pauses in fighting, then move to southern Gaza, where there would be another three-day pause, followed by northern Gaza. Peeperkorn added that there was an agreement to extend the pause in each zone to a fourth day if needed.