Afghan President Hamid Karzai has suggested that extremists in Pakistan were likely behind the deadly double bombings that killed at least 60 people at Shia Muslim shrines in Afghanistan on Tuesday.

Karzai, who had to cut short a trip in Europe in order to return to Kabul and meet with families of the victims, has demanded that the Pakistani government arrest those responsible for the unprecedented attacks.

“We will pursue this issue with Pakistan and its government very seriously,” said Karzai while visiting with wounded survivors in a hospital.

Afghanistan takes this very seriously. It is the issue of the life of the people which we will fully follow up with Pakistan.”

A spokesman for Karzai, Aimal Faizi, told Agence France Presse (AFP) news agency that the president will “demand Pakistan take executive measures… so that justice can be done.”

The killings have prompted fears that sectarian violence between Shias and Sunni Muslims could erupt in Afghanistan --- much like they have in Iraq.

(Pakistani Muslims are predominantly Sunni.)

AFP reported that Karzai had specifically blamed the Lashkar-e-Jhangvi (LeJ) militant group for Tuesday’s wave of deaths.

“Lashkar-e-Jhangvi is based in Pakistan, therefore the government of Afghanistan with all its strength and international support will pursue this issue, Afghanistan cannot ignore the blood of its children,” said Karzai.

The Wall Street Journal reported that LeJ took responsibility for the attacks.

LeJ has been blamed for killing hundreds, perhaps thousands, of Shias in Pakistan. They're also allegedly linked to both al-Qaeda and the Pakistan Taliban.

Reportedly, LeJ has also been connected to the Pakistani intelligence network and might have been behind the sensational beheading of American journalist Daniel Pearl in 2002. Some reports indicate LeJ sought to assassinate former Pakistani president Pervez Mussharraf.

If LeJ is indeed behind the recent attacks, it would raise alarm bells since the militant group has apparently never carried out any such acts in Afghanistan before.

According to The Wall Street Journal, a senior Afghans security officials went even further, accusing Pakistan’s notorious spy agency, ISI, of orchestrating the attacks.

ISI is directly involved in the attack, he said. The main purpose is to spark sectarian violence among Afghans. The militants have used every single tactic in the war, but have failed -- and now this was their new tactic and they successfully carried it out.

On a broader basis, Afghan officials (including Karzai himself ) have long blamed Pakistan -- directly or indirectly – of being behind much of the violence in Afghanistan in order to keep the country unstable.

On Wednesday – there was even more killing in Afghanistan, as another 19 people were killed when a roadside bomb exploded in Helmand province in the southern part of the country.