The explosion ripped through a busy market area, killing 89 people - mostly Shiites from the minority Hazara ethnic group - and injuring dozens of others.
Many of the Hazaras originally fled persecution in Afghanistan but have been repeatedly targeted by Sunni extremists in Pakistan.
Relatives of the victims are maintaining they will not bury the dead until the perpetrators are brought to justice, in protest at what they say is a lack of protection by authorities.
Saturday's attack was the second massive blast that targeted the Hazaras in Quetta this year.
In January more than 100 people were killed when twin blasts destroyed a snooker hall.
The Sunni militant group Lashkar-e-Janghvi has claimed responsibility for both attacks.
The Pakistani government has been accused of turning a blind eye to the activities of militants, but with pressure mounting, the police have conducted a sweep of people with known links to the group.
They have arrested 170 suspects, while four were killed in a shootout with police.
Pakistan's prime minister Raja Pervez Ashraf says the operation is aimed at "eliminating those responsible for playing with innocent people's lives".
The anger felt by the Hazara community is shared across Pakistan.
In the capital, Islamabad, human rights activists as well as representatives from all Pakistan's religious communities lit candles for the victims.
The chairman of the Pakistan Interfaith League, Sajid Ishaq Sindhu, says all Pakistanis need to stand together to defeat extremism.
"Today we are not gathered on the basis of religion, but we are gathered on the basis of humanity because we believe that we are all human beings first, and then we are Muslims, Christians, Hindu and whatever," he said.
"Today we have Christians, we have bishops here, we have pastors, we have Muslim friends here, we have Hindus and Sikhs. It is a symbol of our unity. It's a symbol that people of Pakistan belong to one family."
'You are harming Pakistan'
Pakistan's cricketer legend-turned-politician Imran Khan also called a press conference to vent his anger at the militants who claimed responsibility.
"I tell you by name, Lashkar-e-Janghvi, I tell you by name that this terrorism that you are carrying out in the name of Islam, there can be no bigger enemy of Islam than you," he said.
"Islam is the name of humanity. What you are doing to a different sect of your own religion is something you should not be doing to atheists.
"I strongly condemn you. I also strongly condemn you on behalf of the Pakistani nation. And I say that this terrorism, that through this that you are carrying out, you are harming Islam, you are harming Pakistan."
Lashkar-e-Janghvi has stepped up suicide bombings and shootings on Shiite Muslims in a bid to destabilise Pakistan and install a Sunni theocracy.
Experts say it is a strategy similar to that used by Al Qaeda to try to trigger a civil war in Iraq several years ago.