Bomb attacks in Pakistan and Afghanistan killed 25 people, including police officers.
In Pakistan's western city of Quetta, a suicide bomber killed at least 15 people, 13 of them among police officers, having targeted a polio eradication centre in the city.
The death toll is feared to increase.
Jundullah, a militant group which has links with the Pakistani Taliban claimed responsibility for the attack. The group has pledged allegiance to Islamic State (IS) as well.
Campaign teams in Pakistan working to immunise children against the virus are often targeted by Taliban and other militant groups, according to India Today.
The groups say the campaign is "a cover for Western spies, or accuse workers of distributing vaccines designed to sterilise children”.
In Afghanistan, a suicide attack targeting the Pakistani consulate in the provincial capital Jalalabad killed six people in Nangarhar, including four security officers.
Three attackers had been killed, including the one who had detonated explosives on his body at 9 a.m, Attaullah Khyogani, said spokesman for the governor of Nangarhar province.
Jalalabad is an attraction point for Pakistani residents involved in trade. Moreover, the Nangrahar region has been witnessing clashes between IS and Taliban, as well as government forces' operations, where Afghani wing of the IS mostly strengthen itself.
In capital Kabul, on the other hand, a suicide bomb attack killed four people targeting the Pakistani Consulate.