PESHAWAR: At least seven people were killed and nine others injured Wednesday in an explosion near a police vehicle on its way for security duty for polio immunisation workers in Khyber Pakhtunkhwa's Charsadda district.

The dead included six policemen and a bystander child.

Wednesday’s attack comes only a day after the immunisation drive in Karachi was suspended following the attack on a vaccination team in the city's Qayyumabad area.

The Charsadda police control room confirmed that the police van was attacked in Sardheri bazaar as it was on its way for security duty for an immunisation team.

The police mobile van was destroyed in the blast.

Deputy Inspector General of Police Mardan Range Saeed Wazir said that the bomb, weighing four to five kilograms, was planted on a cycle. He added that the IED was remotely detonated and left six police officials and a child dead.

The injured have been shifted to District Hospital Charsadda for treatment.

In another incident in Punjab province's Bhakkar district, the vehicle of a polio vaccination team came under attack.

The attack left the windows of the vehicle shattered, injuring the driver of the vehicle and a Lady Health Worker.

On Tuesday, three health workers were killed in an attack on a polio vaccination team in Karachi. After the attack in Karachi, the latest in a series of deadly assaults on vaccination teams, the provincial polio workers' association said it was halting operations across Sindh province.

The attacks came just days after the World Health Organisation (WHO) warned that Pakistan's northwestern city of Peshawar was the world's “largest reservoir” of the polio virus.

Pakistan is one of only three countries in the world where polio remains endemic, along with Afghanistan and Nigeria. Efforts to eradicate it have been seriously hampered by the deadly targeting of vaccination teams in recent years.

Militant groups see vaccination campaigns as a cover for espionage, and there are also long running rumours about polio drops causing infertility.

According to the WHO, Pakistan recorded 91 cases of polio last year compared with 58 in 2012. So far, four new polio cases have been recorded in 2014.