Police official Mohammed Sultan said on Saturday that about 150 people were wounded and some remain critical after the attack claimed by the Pakistani Taleban in the southwestern city of Quetta.
Police say Shiite leaders called a general strike in Quetta and all schools are closed for a day in mourning.
The procession of about 2,500 people spearheaded by the Imamia Students Organization was part of multinational celebration of Al-Quds Day to express solidarity of the cause of Palestinians.
When the marchers reached Meezan Chowk of Quetta, suicide bombers struck.
The Al-Qaeda-linked Taleban has taken responsibility for the attack, saying it was revenge for killings of Sunni preachers by Shiites.
"We take pride in taking responsibility for the Quetta attack," Qari Hussain Mehsud, the mentor of Taleban suicide bombers, told Reuters by telephone from an undisclosed location.
The attack was the third in a day. The first was a roadside bombing in the northwestern city of Peshawar that killed one police officer and wounded three others.
Hours later, a suicide attack on a mosque belonging to the minority Ahmadi sect killed at least one person and wounded several others in the nearby town of Mardan.
In the Quetta carnage, dozens of dead and wounded lay in pools of blood after the blast that also engulfed vehicles in flames.
Protesters dragged wounded people into private cars as burning motorcycles sent clouds of black smoke billowing through the streets. The bodies of the dead and wounded lay strewn across the road.
Some Shiite youths fired in the air after the blast, and Qazi Abdul Wahid, a senior police official, said officers were trying to control the situation.
Local media reports said angry mobs started firing automatic weapons soon after the explosion. Shopkeepers shuttered down, turning the city into a virtual "ghost town."
Inspector General of Baluchistan Malik Iqbal said police had provided sufficient security but the marchers violated security procedures.
"The procession was not allowed to deviate from the route given to them by police. But the people in the procession violated standard operating procedures of security agencies. They were not supposed to go to Meezan Chowk and even the organizers of the procession had given in writing that they would follow security code," he said.
Pakistani Taleban commander Qari Hussain Mehsud told The Associated Press one of his suicide bombers carried out the attack.
"We proudly take its responsibility," he said. "Our war is against America and Pakistan security forces, but Shiites are also our target because they too are our enemies."
He said he was proud the US had added the Pakistani Taleban to its international terrorism blacklist on Wednesday, and he threatened attacks in the US and Europe in coming days that would resemble a recent attempted car bombing in Times Square.
The attack in Quetta was the week's second claimed by the Pakistani Taleban and targeting Shiites, who by some estimates make up about 20 percent of the population in the mostly Sunni Muslim country, although figures are imprecise and disputed.
A triple suicide attack Wednesday night killed 35 people at a Shiite ceremony in the eastern city of Lahore.
Shiite leaders blamed the government for failing to protect them and called a general strike in Quetta, where all schools were closed for a day of mourning. Shiites make up an estimated 20 percent of the population in the mostly Sunni Muslim country, although figures are imprecize and disputed.
Long-standing sectarian violence in Pakistan, particularly against Shiites, has been exacerbated by the rise of the Sunni extremist Taleban and Al-Qaeda movements.
Interior Minister Rehman Malik said the Taleban, Al-Qaeda and the outlawed Lashkar-e-Jhangvi militant group were working together to destabilize Pakistan.
"They are infidels," he told reporters in Islamabad.
Pakistan's weak civilian government is struggling to deal with massive flooding and the incessant militant violence aimed at overthrowing the Western-backed administration.
White House press secretary Robert Gibbs said the timing of the recent attacks — during the Muslim holy month of Ramadan and as Pakistan recovers from the flooding — made them "even more reprehensible."
The flooding began with unusually heavy rains in the country's northern mountains and killed more than 1,600 people. Millions have been driven from their homes and the waters are still swamping rich agricultural land in the southern provinces of Sindh and Punjab.
United Nations Secretary-General Ban Ki-moon strongly condemned the terrorist bombings. "These attacks, which deliberately targeted Shiite Muslims and killed or injured scores of civilians, are unacceptable," UN associate spokesman Yves Sorokobi said at UN headquarters in New York.
The Taleban-allied Haqqani network controls the northwestern tribal area of North Waziristan along the Afghan border but its fighters are hunted by US drone aircraft that regularly unleash deadly missile attacks.
Two Pakistani intelligence officials told the AP three missiles hit a house in a village near Miran Shah, the main town in North Waziristan, Friday evening.
The officials, who spoke on condition of anonymity because they were not authorized to release the information to the media, said the identity of the slain was not immediately clear.
The officials said a second suspected US missile strike killed two people in a vehicle in the North Waziristan village of Datta Khel. They said the men were believed to be foreign militants.
