The bomber struck at a time when over 200 mourners had gathered at the government-run Civil Hospital in Quetta where the body of prominent lawyer Bilal Anwar Kasi, who was shot dead earlier in the day, was brought. Kasi was the president of Balochistan Bar Association.
A loud explosion was heard at the emergency department where Kasi's body was brought for an autopsy.
"No crater found at the site of the attack and it appears the bomber had the explosives strapped to his chest," a police officer said.
Bomb Disposal Squad officials also confirmed the explosion was a suicide bombing.
A spokesman for Jamaatul Aharar, a faction of Tehreek-e-Taliban Pakistan, said that his faction "accepts responsibility" for the attack in the southwestern city of Quetta and vowed more attacks "until the imposition of an Islamic system in Pakistan".
"The Tehreek-e-Taliban Pakistan Jamaat-ur-Ahrar takes responsibility for this attack, and pledges to continue carrying out such attacks. We will release a video report on this soon," spokesperson Ehsanullah Ehsan said in an email to media outlets.
Doctors and rescue officials put the death toll at 75 and said the number could increase as the condition of some of the injured was very critical. They said 115 people were injured in the attack.
Balochistan Home Minister Mir Sarfaraz Bugti said the suicide bomber had blown himself up at the entrance of the hospital as many lawyers and mourners had gathered to receive the body of slain Kasi.
"It was a well coordinated and planned suicide attack with the aim to cause maximum damage," he said.
The dead included a cameraman for a local television channel while another cameraman and reporter of another channel were also wounded in the blast.
Barrister Ali Zafar of the Balochistan bar association said that majority of the dead or injured were lawyers.
He said the former president of Balochistan Bar Association Baz Mohammad Kakar was injured in the blast.
Police surrounded the hospital and cordoned off the area
after the blast. An emergency was declared in hospitals across Quetta and several injured were shifted to other hospitals for treatment.
The troubled Baluchistan province has been hit by terror attacks by militants and separatists who demand more autonomy in the province. Outlawed outfits have also carried out sectarian killings of Shia Hazaras and targeted police and security officials.
Television footage showed scenes of chaos with panicked mourners struggling to leave the scene as debris and smoke filled the corridors of the hospital's emergency ward. Many of the victims were clad in the black suit worn by lawyers.
"Today's suicide attack appeared to target Kasi's supporters," Anwar ul Haq, a spokesman for the Balochistan government, said.
Prime Minister Sharif and President Mamnoon Hussain strongly condemned the attack. Sharif ordered the provincial government to arrest the culprits.
"No one will be allowed to disrupt the peace of the province," Sharif said. He cancelled all prior commitments and visited Quetta.
The provincial government also announced a three-day mourning during which Pakistan's National Flag will remain at half mast on government buildings.
Social networking site Facebook activated its "safety check" feature after the blast in the provincial capital. Officials said mobile phone jammers had been activated around hospitals in the area.
Pakistan's army chief Raheel Sharif said that all necessary steps would be taken to defeat militancy in the country as he chaired security meeting in Quetta.
He said that attack was an attempt to undermine improved security in Balochistan. He said it was attempt to target China-Pakistan Economic Corridor (CPEC).
Raheel ordered intelligence agencies to carry out country-wide special combing operations to target terrorists in the wake of recent terror attack in Quetta.
The international community condemned the terror strike.
"On behalf of the US Mission to Pakistan, I strongly condemn today's horrendous and despicable attacks in Quetta, the murder of Bilal Kasi, the Balochistan Bar Association President and the bombing at the Civil Hospital. I extend my deepest condolences to the victims and their families during this time of grief," American Ambassador David Hale said.
The EU also condemned the assault.
