News of the attack spread quickly after a geo-tagging mistake by Facebook, which accidentally prompted users around the world to confirm they were safe following the attack.

Pakistan has suffered significantly from extremist groups. A Taliban insurgency operates against the government with impunity along the country’s border with Pakistan. The country’s apparent instability, combined with a nuclear arsenal, has made it a constant source of anxiety for anti-terror officials.

Lahore is the capital city of the province of Punjab in northwest Pakistan; one of the country’s richest cities, it is also the home of Nawaz Sharif, Pakistan’s prime minister.

Punjab’s governor was murdered by one of his own bodyguards in 2011 after contemplating a plan to loosen blasphemy laws seen as targeting the country’s non-Muslim minorities. The bodyguard, Malik Mumtaz Hussain Qadri, was executed last month but his death became a rallying cry for Islamists, including during on-going street demonstrations this weekend.

In Islamabad, Pakistan’s capital, Qadri’s supporters have become increasingly violent and the army have been dispatched to restore order.  A source in the city says there is chaos near parliament and protesters are setting fire to buildings. “Anyone watching TV immediately connected the incidents,” she told Quartz.

Saquib Tanveer, a senior researcher for Geo TV who is on the scene, told Quartz that one thousand protestors have been arrested, while dozens of police officers and protestors have been injured.

The government has already declared three days of mourning after the Lahore attack.

Update, March 27, 3:20pm: The post was revised to show the updated number of deaths and to include the news that a group has claimed responsibility.

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