Pakistan's military says it has killed more than 100 suspected militants in nationwide raids following a shrine explosion claimed by Islamic State.

The suicide bombing on Thursday was the deadliest attack in the country for two years, killing at least 88 people and injuring 343 others.

IS said it targeted a "Shia gathering" and it was the latest in a series of atrocities across Pakistan this week.

Authorities have faced criticism for failing to tighten security before the bomber struck at the Lal Shahbaz Qalandar shine in southern Sindh province.

There are fears IS has become stronger in Pakistan, helped by homegrown militants who can hide in neighbouring Afghanistan.


Image: Worshippers at the Lal Shahbaz Qalandar shrine following the blast

Government officials in Islamabad have accused the Kabul government of ignoring earlier pleas to crackdown on hideouts and it wants 76 "terrorists" handed over.

The violence highlights the threat from groups like the Pakistani Taliban and IS, and analysts have warned of a big escalation in militants' attempts to destabilise the region.

Imtiaz Gul, head of the independent centre for research and security studies in Islamabad, said: "This is a virtual declaration of war against the state of Pakistan."

PM Nawaz Sharif's foreign policy adviser Sartaj Aziz blamed Jamaat-ur-Ahrar (JuA), a Pakistani Taliban faction linked to Islamic State, for the shrine bombing.

Image: Police at the site of the shrine bombing

Most of the other recent attacks have been claimed by factions of the Pakistani Taliban.

It is also waging a fight against the government but some of its fighters have cooperated with IS as well as defected to the jihadist group.

Following the shrine blast, witness Anwer Ali rushed to the scene and described seeing dead bodies and chaos as people fled.

He said: "There were threats to the shrine. The Taliban had warned that they will attack here, but authorities didn't take it seriously."