Sunday's attack on worshipers cane a day after the Taliban leader asked his fighters not to harm civilians [EPA]

At least seven people have been killed after a suicide bomber blew himself up in Afghanistan's northern Baghlan province.

Police said the bomber targeted worshippers returning from the Eid al-Adha prayer marking the beginning of one of the largest Muslim holidays.

At least six civilians and one police officer were killed in Sunday's attack.

The bomber struck as worshippers were exiting a mosque in Baghlan province's Old Baghlan City and were congratulating each other on the start of the festivities, said Lal Mohammad Ahmadzai, spokesman for the regional police commander in the north.

Ahmadzai said at least 20 other people were wounded in the blast.

Sediq Sediqqi, spokesman for the Afghan interior ministry, said on Twitter that a second suicide bomber had been arrested.

No one has taken responsibility yet, but Seddiqi said "police initial investigation shows that the suicide bombers were Taliban".

Protecting Civilians

The attack came a day after Mullah Omar, leader of the Afghan Taliban, urged his fighters to avoid civilian casualties in their campaign against the government and foreign forces.

In a message released on the Taliban's website, Omar said he believed conflicts such as the decade-long Afghan war were resolved by "realisation and understanding". 

"Do not wrongly pester and daunt anyone by the barrel of the gun," the statement in Omar's name said in English. "The mujahideen have to take every step to protect the lives and wealth of ordinary people."

The statement threatened punishments under Islamic law for fighters responsible for civilian death

As the US-led NATO force and its Afghan partners have focused their operations on Taliban strongholds in the south and east, armed fighters have carried out an increasing number of assaults in the north, including targeted attacks against leaders associated with the former Northern Alliance.

The Northern Alliance is a coalition which resisted the Taliban takeover of Afghanistan in 1996.

At least five Northern Alliance leaders have been killed this year, including Burhanuddin Rabbani, the former president; General Daud Daud, the police commander of the northern zone; as well as three provincial police chiefs and one provincial governor.

Source: Al Jazeera