A blast has also rocked the provincial health department headquarters but left no casualties.

Ghulam Dastagir Nazari, head of the immunisation program at Afghanistan's Health Ministry said the explosion took place at the entrance to the health department for the province of Nangarhar late on Tuesday morning.

Around the same time unknown gunmen shot vaccination workers at two separate locations in Jalalabad, killing two volunteers and one supervisor in the polio immunisation program, he said.

It was not immediately clear who carried out the two separate shootings on Tuesday.

A number of assassinations have taken place in urban centres since peace talks between the insurgent Taliban and the Afghan government began last year in Doha, many of them targeting professional women as well as government employees, media and civil society members.

Three female journalists were killed in Jalalabad this month, an attack claimed by Islamic State.

The government blames most targeted killings on the Taliban, who deny involvement.

The attacks came the same week the polio vaccination campaign for 2021 kicked off. The programme is led by the health ministry with the involvement of the United Nations' children's agency UNICEF.

Afghanistan and neighbouring Pakistan are the only two countries where the crippling disease is still endemic.

Militant groups including the Taliban have targeted health workers in the past.

The UN mission to Afghanistan warned last year that health workers were increasingly at risk after a series of attacks.

One attack on a Kabul maternity ward in May killed 24 people, including mothers and newborn babies.

Australian Associated Press