A faction of Pakistan-based sectarian militants Lashkar-e-Jhangvi have claimed responsibility for twin bombs that hit a market in the northwestern town of Parachinar, killing at least 50 people ahead of the holiday marking the end of Ramadan.
LeJ's Al Alami faction said in a statement it was targeting minority Shi'ite Muslims and threatened more attacks over Pakistanis fighting against Sunni militants in Syria's civil war.
Video footage after the attack showed civilians dragging bleeding victims outside to waiting ambulances in the chaos that came when the bombs exploded before the sundown meal breaking the daily Ramadan fast.
"We have received 50 bodies so far, and 250 were wounded," said Sabir Hussain, medical superintendent of Parachinar Hospital. Sixty of the seriously wounded had been transferred to the larger city of Peshawar, he added.
LeJ Al Alami, which has previously partnered with Middle East-based Islamic State to carry out attacks in Pakistan, said it has previously "warned the Shia community of Parachinar ... to stop staining your hands with the blood of Sunnis in Syria".
It repeated the demand in the statement, saying that "otherwise in the coming days you will face such hate-fuelled and deadly attacks that you will not be able to stand them".
Hundreds of Pakistanis - many of them Shi'ites believed recruited by Iran - have gone to fight in Syria to defend the government of Tehran's ally, President Bashar al-Assad.
Assad's government is also supported by Russian air strikes and fighters from Lebanon's Hezbollah militia, against an array of Sunni rebels backed by Turkey and Arab states.
The United States, Turkey, Arab and European powers are also participating in a coalition bombing Islamic State, a Sunni Muslim militant group.
The market bombings in Parachinar late on Friday afternoon came on a particularly deadly day for Pakistan as both Sunni and Shia Muslims prepared to mark the Eid al-Fitr holiday marking the end of the holy fasting month of Ramadan.
Another bombing in the southwestern city of Quetta killed 13 people and a drive-by shooting killed four police officers in the southern megacity of Karachi on Friday. Both of those attacks were claimed by another militant group, the Jamaat ur Ahrar faction of the Pakistani Taliban.
Islamic State also claimed the Quetta attack through a messaging network. It had not commented on the Parachinar attack by Saturday afternoon.
Sunni-majority Pakistan also has a sizeable Shi'ite minority and has sought to avoid being dragged into sectarian strife that is rife in Syria and also the recent rift between Qatar and Saudia Arabia-led Sunni states that have cut off ties with Doha in part over its relations with Iran.
Pakistan's military said late Friday it had tightened security across the country, including at the Afghan border, following the attacks.