Islamabad ( CNN ) -- A campaign to eradicate polio from the northwest tribal region of Pakistan is on hold after fatal attacks on health workers vaccinating children , the Balochistan government said Tuesday . Six polio vaccination workers were killed in attacks in Pakistan since Monday , the World Health Organization and Pakistani police told CNN Tuesday . Another attack last July wounded a WHO doctor and his driver while they worked on the polio campaign in Karachi . Read more : At the U.N. , a vow to eradicate polio by 2015 . The motive for the attacks was unclear . However , Pakistanis have viewed polio vaccination campaigns with suspicion after the CIA 's use of a fake vaccination program last year to collect DNA samples from residents of Osama bin Laden 's compound to verify the al Qaeda leader 's presence there . Bin Laden was killed by U.S. forces in May 2011 . In June , a Taliban commander in northwest Pakistan announced a ban on polio vaccines for children in the region as long as the United States continues its campaign of drone strikes in the region , the Taliban said . `` Polio drops will be banned in North Waziristan '' until the strikes cease , according to a Taliban statement . North Waziristan is a tribal region of Pakistan near the border with Afghanistan . Read more : WHO doctor attacked during Pakistan polio campaign . The vaccination campaign has been suspended indefinitely in Quetta , Killa Abdullah and Pishin districts , Balochistan government spokesman Noor ul Haq Baloch said . `` The reason behind suspension of the campaign is the security threat to workers , '' Baloch said . `` At least six people working on a polio vaccination campaign have been reported shot dead in several locations in Pakistan -- Gadap , Landi , Baldia and Orangi towns of Karachi city , Sindh Province and Peshawar , Khyber Pakhtunkhwa Province , '' a WHO statement said . `` Those killed were among thousands who work selflessly across Pakistan to eradicate polio . '' WHO earlier estimated that 280,000 children living in the tribal area were in need of polio vaccinations . Read more : Taliban 's vaccine ban may affect 280,000 children . `` Polio is a highly infectious disease caused by a virus that can cause permanent paralysis in a matter of hours , '' WHO said . `` Safe and effective vaccines protect children from the disease . Currently the disease remains endemic in only three countries : Afghanistan , Nigeria and Pakistan . '' Health officials confirmed four cases of polio in Balochistan in 2012 , while 11 cases of polio 2 virus were reported there , Baloch said . There were 73 cases of polio virus in 2011 , he said . Four female health workers were shot to death in Karachi Tuesday morning , including two women killed after administering the vaccination to children , according to Naeem Shah , a senior police official . Two other women were shot while going house to house giving vaccinations in Peshawar , police official Javed Khan said . Gunmen opened fire on the women as they left a house where they had vaccinated children , he said . Pakistan Prime Minister Raja Pervez Ashraf ordered his interior ministry to work with the polio eradication project to `` provide foolproof security to the polio teams . '' CNN 's Nasir Habib in Islamabad contributed to this report .
Six polio vaccination workers were killed in attacks in Pakistan since Monday . A Taliban commander in northwest Pakistan banned polio vaccines . Pakistan is one of 3 countries where polio remains endemic , WHO says . WHO estimates 280,000 children living in the northwest tribal area need of polio vaccine .