The death toll from the suicide attack at the shrine of Sufi saint Lal Shahbaz Qalandar climbed to 83 on Friday evening with more than 250 injured, as a country-wide crackdown on militants launched after the savage attack intensified.

Prime Minister Nawaz Sharif and Chief of Army Staff General Qamar Javed Bajwa reached Sehwan and were briefed about the situation in the city by the top security officials. Later they visited the injured in Nawabshah.

Sindh Chief Minister Murad Ali Shah had reached Sehwan, his political constituency, on Thursday night.

'Security lapse'

The militant Islamic State group (IS) had claimed the attack, which also injured more than 200.

The bomber had struck as devotees gathered for the evening dhamaal ritual in a crowded space within the shrine.

The Sindh's inspector general of police termed the attack a result of a "security lapse".

Police had cordoned off the Lal Shahbaz Qalandar shrine early Friday, as forensic investigators arrived.

Security for shrines was tightened across the country in the aftermath of the bombing, with some closed till further notice and entry to others tightened considerably.

Read: 70 dead as bomb rips through Lal Shahbaz shrine in Sehwan

Lack of medical facilities

The popular shrine's white floor was still smeared with blood on Friday morning, with scattered debris including shoes, shawls, and baby bottles. At least 20 children are believed to be among the dead, the head of Sehwan's medical facility Moeenuddin Siddiqui said.

The Sindh government announced three days of mourning as citizens vented their grief and fury on social media, bemoaning the lack of medical facilities to help the wounded, with the nearest main hospital some 130 kilometres from the shrine.

The medical facilities in Sehwan are basic, and many of the injured were flown to Karachi and other major cities of Sindh in military planes and helicopters.

The country had seen a dramatic improvement in security in the past two years, but multiple attacks this week have undermined the growing sense of optimism.

Resurgence in terror attacks

Pakistan seems to be experiencing a fresh resurgence in terror attacks.

The bombing at Qalandar's shrine was the tenth militant attack over the past five days in the country. The fresh wave of terrorism started with an attack on a DSNG van of Samaa TV in Karachi on Sunday, leaving a media worker dead.

The next day saw a suicide attack in Lahore, killing 13 people, including two senior police officers. On the same day, a Bomb Disposal Squad commander and a policeman were killed while defusing a bomb in Quetta and two security personnel lost their lives when their vehicle hit a landmine in South Waziristan.

On Wednesday, four suicide bombers blew themselves up in Peshawar, Mohmand Agency and Charsadda in an attempt to target security forces and members of the judiciary.

On Thursday, three soldiers were killed in a bomb attack in Awaran area of Balochistan, and four policemen and a civilian were killed in an attack on a police van in Dera Ismail Khan.