According to details, the explosion took place in the parking area of Gulshan-e-Iqbal Park leaving 74 people were dead while more than 300 people were wounded.
Witnesses described children screaming as people carried the injured in their arms, while frantic relatives searched for loved ones.
Scores of the injured persons, including women and children, are said to be in critical condition.
A stampede broke out following the explosion due to which many children got separated from their parents.
Doctors described frenzied scenes at hospitals, with staff treating casualties on floors and in corridors, as officials tweeted calls for blood donations.
Witnesses said the wounded were first rushed to hospital in rickshaws and other vehicles before dozens of ambulances arrived on the scene.
Lahore‘s top administration official, Muhammad Usman, said 65 people had been killed in the suicide attack, and more than 50 children were among the injured.
Facebook activated its safety check system, so people could tell friends and relatives they were safe, but a glitch meant notifications were sent to people all over the world.
The company later apologised, but some users said the error meant news of the attack spread more quickly than it might otherwise have done.
Prime Minister Nawaz Sharif expressed his “grief and sorrow over the sad demise of innocent lives”.
While Indian PM Narendra Modi telephoned to say “the people of India stand with their Pakistani brethren in this hour of grief,” state media reported.
The US labelled the incident “cowardly”, while Pakistan’s Nobel Peace Prize winner Malala Yousafzai tweeted: “Pakistan and the world must unite. Every life is precious and must be respected and protected.”
The affected persons are being treated at Shaikh Zayed Hospital and Jinnah Hospital for medical attendance.
Many of the wounded persons are being treated on the hospital floors due to shortage of beds in the medical facility.
Emergency has been imposed in all medical facilities of the historical city.
Five to six kilograms of explosive materials was used to carry out the terrorist attack.
دھماکے سے پارک میں بھگدڑ، ڈی آئی جی آپریشنز حیدر اشرف کہتے ہ…دھماکے سے پارک میں بھگدڑ، ڈی آئی جی آپریشنز حیدر اشرف کہتے ہیں دھماکہ خودکش لگتا ہے، جوگیٹ نمبر ایک کےقریب پارکنگ ایریا میں ہوا
Posted by ARY News on Sunday, 27 March 2016
It is being said that large number of people were present in the Gulshan-e-Iqbal Park due to the weekend and Easter celebrations.
A high-level meeting was also held hours after the attack to probe whether the suicide attack was linked to the capture of RAW agent in Balochistan.
Condolences pour in
Australia condemns the terrorist attacks in Lahore. Our condolences, prayers & solidarity are with the victims & their family & friends.
— Malcolm Turnbull (@TurnbullMalcolm) March 27, 2016
Due to this merciless attack in my country, I have ceased all work commitments tonight. My heart is with my hometown. Stay strong #Lahore
— Wasim Akram (@wasimakramlive) March 27, 2016
Strongly condemn the terrorist attack in Gulshan e Iqbal Park #Lahore. My heartfelt prayers go to the victims.
— Siraj ul Haq (@SirajOfficial) March 27, 2016