The campaign, targeting 39,000 children, was initiated under huge international pressure to vaccinate every child in the country, despite more than two years of a dangerous security situation in the region.
“The campaign has been started in the region where military is not fighting against the militants. There is no timeframe for this campaign and it will continue until we vaccinate all 39,000 children,” doctor Sadiq Khan, in charge of the health department in North Waziristan, told AFP.
Andnan Khan, a government spokesman, told AFP that the authorities had not set a timeframe for the campaign due to the security situation.
On Tuesday, a similar campaign was started in the neighbouring South Waziristan tribal district along the Afghan border.
A day later, gunmen killed four members of a polio vaccination team in the outskirts of Quetta city, the capital of southwestern Baluchistan province.
Pakistan is one of only three countries where polio remains endemic. Attempts to stamp it out have been badly hit by opposition from militants and attacks on immunisation teams, which have claimed more than 60 lives in the last two years.
The militants have in the past claimed that the polio vaccination is a cover for espionage or a Western conspiracy to sterilise Muslims.
Officials say the number of polio cases recorded in Pakistan has reached 246 for the year — a 14-year high and more than double the total for the whole of 2013.
Among the new cases detected, 136 are in the troubled northwestern tribal areas at the border with Afghanistan, the stronghold of Taliban and Al-Qaeda militants.
The outbreak led the World Health Organization earlier this year to ask Pakistan to impose mandatory vaccinations on travelers leaving the country.
The Pakistani military launched a major offensive in the North Waziristan district in June and say they have killed more than 1,500 militants so far, with 125 soldiers losing their lives.