Shia Muslims have delayed the burial of most of the 43 people killed in Tuesday's attack in south-west Pakistan in protest at arrests of Shia youths.
Shops, cars and offices were burned by mobs after the attack
About 15 people were detained in Quetta after reprisal attacks, although Shias later reportedly secured their release and set the funerals for Thursday.
Authorities in Pakistan have ordered an inquiry into the attack on a procession on the holy day of Ashura.
Pakistan's Shia minority and majority Sunnis have a history of clashes.
Hundreds of Shia mourners gathered at a mosque in Quetta on Wednesday, wailing and beating their chests in mourning for those killed.
Leaders of the community said Shias had been arrested when they went to hospitals to donate blood.
"The Quetta incident has exposed the government's claim of taking foolproof security measures in the country for the protection of mourners," said Shia leader Tanveer ul-Kazim.
"We are feeling insecure and unsafe."
The leaders were still meeting late on Wednesday and agreed to bury the dead on Thursday.
They were preparing to present new demands to the authorities which they refused to specify although it is thought they include the transfer of some provincial and local officials.
The precise events of Tuesday's attacks are still unclear.
One Quetta-based intelligence officer told the AFP agency that two gunmen fired on the procession from the top of a building while a suicide bomber blew himself up.
Two other gunmen started firing at ground level, sparking deadly police crossfire, the officer said.
Another source said there were 13 attackers, while Quetta's deputy police chief Arif Akram said two of them had explosives strapped to their bodies.
One suspect was beaten by a mob and handed over to police, reports said.
At least five policemen are among those reported dead.
No group has said it carried out the attack, but Shia leaders suspect Sunni extremists, possibly from the outlawed Lashkar-e-Jhangvi group.
Automatic gunfire created chaos in the procession
Witnesses said the attackers' guns were painted with the Lashkar-e-Jhangvi name.
Foreign ministry spokesman Masood Khan condemned the attacks.
"In Quetta the ugly face of terrorism has reared its head once again. These are heinous and hideous crimes. Our investigations will be comprehensive and thorough."
A curfew is still in place in Quetta, with soldiers patrolling its streets.
Homes, businesses and a mosque used by Sunni Muslims were torched by rioters following the killings.
Security forces fired shots and tear gas to disperse them.
SHIA FESTIVAL: ASHURA
Annual Shia festival commemorating martyrdom of Imam Hussein
Hussein, grandson of Prophet Mohammad, killed at Karbala by army of Caliph Yazid in 680
Faithful strike themselves with chains and swords to atone for Hussein martyrdom
The murder 19 years earlier of Ali, Hussein's father, gave rise to the central schism in Islam between Sunni and Shia
Late into Tuesday night, firefighters tackled blazes set off by rioters. About 60 shops, a cinema and a bank were burned.
Security had been tight on Tuesday for Ashura, following a similar attack on a Shia religious gathering in Quetta in July last year that left 50 people dead.
Tuesday's attack coincided with devastating explosions in the Iraqi cities of Baghdad and Karbala that left scores dead - these too targeted Shias who had been celebrating Ashura, the anniversary of the death of the Prophet Muhammad's grandson.
In a separate incident on Tuesday, a stampede left 13 Muslim women and children dead in the town of Parachinar, 250km (155 miles) west of the capital, Islamabad.
Local officials said a short circuit plunged a mosque into darkness, causing panic.
"Dozens of women and children crammed on a staircase which collapsed under the pressure," said Parachinar official Azam Khan.
Another two people died in a shooting incident during a Shia procession in Punjab province. Forty more were injured following clashes between Shias and Sunnis in the town of Phalia, 600km north-east of Quetta.