Twin blasts in Kabul and the northern city of Mazar-e-Sharif aimed at Afghanistan's minority Shiite Muslims killed nearly 60 people on Tuesday as they celebrated Ashura, one of their sect's holiest days, signaling, perhaps, a new sectarian turn in what was one of the war's deadliest attacks.

A spokesman for Lashkar-e-Jhangvi, a Sunni militant group based in Pakistan, claimed responsibility for the attacks, Fox News reported, though the claim couldn't be independently verified.

A suicide bomber blew himself up in a crowd of men, women and children gathered outside the shrine. The Public Health Ministry said 56 people were killed and more than 160 wounded. In the second attack, a bomb on a bicycle exploded as a convoy of Shiites passed on a road in Mazar-e-Sharif, The Associated Press reported. The Interior Ministry said police defused a second bomb planted near the first.

President Hamid Karzai called the attacks unprecedented.

It is the first time that, on such an important religious day in Afghanistan, terrorism of that horrible nature is taking place, Karzai said in Germany, where he attended an international conference on the future of Afghanistan.

Pakistan's Lashkar-e-Jhangvi, which has close ties with Pakistan's Taliban, has been involved in massacres of Shiites. In September, the Lashkar-e-Jhangvi took responsibility for killing 28 Shiite pilgrims near the Pakistani city of Quetta. The Taliban condemned the latest attacks.

In a statement on Tuesday, the Afghan Taliban high command, which calls itself the Islamic Emirate of Afghanistan, said that it will never let anybody take action against our compatriots based on their religious sect, ethnicity or regional origin and blamed the Kabul and Mazar-e-Sharif bombings on the U.S.-led coalition, the Wall Street Journal reported.