Twin blasts at a snooker hall in the south-western Pakistani city of Quetta have killed 81 people and injured more than 120, police say.
Many of the casualties were caused by the second blast as police and media rushed to the scene.
The bombed area is predominantly Shia Muslim, and the Sunni extremist group Lashkar-e-Jhangvi said it had carried out the attack.
Earlier, a bomb in a market area killed 11 people and injured 27 more.
A spokesman for another militant group, the United Baloch Army, said it had carried out that attack.
Balochistan is plagued by both a separatist rebellion and sectarian infighting between Sunnis and Shias.
The Taliban and armed groups that support them also carry out attacks in the province, particularly in areas near the Afghan border. Pakistan's military has been engaged in a long-running battle against those militant groups.
A senior police officer, Hamid Shakil, told Agence France-Presse news agency that a bomb exploded outside the snooker hall building on Alamdar Road and that the second blast occurred 10 minutes later as rescue workers, police and media arrived.
The first blast appeared to have been carried out by a suicide bomber on foot, police said, while the second was a car bombing.
The dead included at least two members of a media team and four workers from a private rescue organisation, the Edhi Foundation. At least five policemen also died.
Home Secretary Akbar Durrani told AFP the bombings were in an area dominated by the minority Shia Muslim community.
Mr Shakil said that many of the dead and wounded were Shia, adding that the death toll could rise.
Lashkar-e-Jhangvi, which is a banned organisation, said it had carried out the attack.
The BBC's M Ilyas Khan in Islamabad says the group has in the past targeted the area's ethnic Hazara Shia.
A senior government official told the BBC he believed the bombings were the group's reaction to two incidents on Wednesday - the shooting of Sunni cleric and the seizure of arms and ammunition from a suspected Lashkar-e-Jhangvi hideout.
TV footage of the earlier market attack showed survivors picking through debris, and emergency crews taking away the wounded.
"Frontier Corps [paramilitary] personnel were the target because the bomb was planted underneath their vehicle," Mr Shakil told AFP.
The dead include one paramilitary soldier and two civilian officers.
Also on Thursday, at least 21 people were killed and more than 80 injured in an explosion near Mingora in Pakistan's north-western Swat valley.
The blast took place at a religious gathering.
Police initially said the explosion was caused by a gas canister, but a senior official later said it was a bomb.
Swat has been controlled by the Pakistani army since it drove out the Taliban in 2009, but the militants still carry out attacks, most notably on schoolgirl campaigner Malala Yousufzai last October.