The suicide bomber blew up his explosives-laden car near Inspector General of Police Ehsan Mehboob's office in Quetta, the capital of Balochistan province, killing at least 13 people, including seven policemen, and wounding 21 others.
The blast was claimed by both the local affiliate of the Islamic State terror group and by Jamaat-ul-Ahrar (JuA), a splinter group of the Tehrik-e-Taliban Pakistan.
Hours later, two back-to-back blasts tore through a market crowded with the people shopping for Eid in the Shia- dominated Parachinar city in the Kurram tribal region, killing at least 30 people, mostly Shias, and injuring 100 others.
The first blast occurred during rush hour in Turi Market, where a bus terminal is also located. The second blast took place as rescuers and bystanders rushed to aid those who had been hurt in the first explosion.
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At least 30 people have been killed and 100 others injured in Parachinar, Dawn news reported.
No group claimed responsibility for the blasts. However, Sunni militant groups have claimed responsibility for several attacks in the area in the past.
In the evening, two armed men on a motorcycle, with their faces covered with helmets, opened fire on police officers at a roadside restaurant in Karachi and killed four of them.
An assistant sub-inspector was among those killed in the attack, said Superintendent of Police Asif Ahmad.
The emergency and rescue services shifted injured to Agency Headquarters hospital Parachinar. The security forces cordoned off the entire area and started search operation.
Pakistan Army contingents and FC personnel reached the site of the attack to aid in rescue efforts.
"Two Army aviation helicopters have taken off from Peshawar to Parachinar for the speedy evacuation of the injured to Peshawar," the army said in a statement.
"Rescue operation in progress," it added.
Army spokesman Major General Asif Ghafoor said that security has been tightened across the country.
"Special Intelligence-Based Operation (IBOs) and search operations (were) launched in coordination with intelligence and other Law Enforcement Agencies," he said.
On March 31, a car bomb blast near an Imambargah of Shia Muslims killed 23 people and injured 70 others in Parachinar.
In January, 25 people were killed and 87 others when a bomb tore through a crowded vegetable market in the same city.
Prime Minister Nawaz Sharif condemned the attacks, saying that terrorists involved in the attacks will be taken to task and all out efforts will be taken to eliminate terrorism.
Balochistan government spokesperson Anwarul Haq Kakar told Geo News that the suspected Quetta bomber tried to break a security perimetre to target the police offices but blew up after policemen standing guard attempted to stop him.
Of the injured, nine are said to be policemen.
Kakar blamed India for the Quetta blast.
DIG Quetta Abdul Razzaq Cheema, addressing the media, said they are examining CCTV footage to determine the details of the incident.
An initial investigation report by Civil Defence Director Aslam Tareen revealed that 75 kilogrammes of explosives were used in the Quetta blast.
Footage of the incident showed two vehicles badly damaged in the explosion, while debris lay scattered on the street.
Officials said the explosion was loud enough to be heard from a distance and shattered windows of nearby buildings.
Earlier this year, on February 13, a blast took place near the Saryab Bridge in Quetta killing two personnel of the bomb disposal squad and leaving 11 injured.
In August, last year, a suicide bomber targeted the emergency services ward at Civil Hospital, following the death of the president of the Balochistan High Court Bar Association, killing at least 70 people and leaving many wounded.