Separatist group Sindhudesh Revolutionary Army claims responsibility for coordinated attacks that also left at least a dozen people wounded.
Three consecutive explosions claimed by a little-known militant group killed four people, including two special forces soldiers in Pakistan's southern province of Sindh on Friday, officials said.
At least a dozen people were also wounded.
Shadowy separatist organisation Sindhudesh Revolutionary Army (SRA), which wants the province to break from the Pakistani federation, said it carried out the attacks.
One of the blasts was in Karachi, Pakistan's largest city and the capital of Sindh, where a civilian died and eight others including a paramilitary soldier were wounded.
That explosion occurred outside a centre for distribution of government cash handouts, and police believe the target was a vehicle of the Sindh Rangers paramilitary force parked outside.
According to local media reports, paramilitary ranger troops were in a market to buy food when the blast took place.
Police said the dead and wounded were transported to a nearby hospital.
The SRA has claimed previous attacks on rangers.
Bomb blast in Karachi, Liaqatabad near Ehsas Emergency Centre.— • S I D R A • (@imran_sidra) June 19, 2020
6 people are injured and one person lost his life..
May Allah SWT keep everyone safe. Aameen.#BombBlast #Karachi #EhsasCentre pic.twitter.com/S6UUb6KtH1
The second blast was reported in Ghotki district, 500 km north of Karachi, where two Pakistani soldiers died along with a passerby, local police chief Furrukh Ali said.
The third blast took place in Sindh's Larkana district, where no casualties were reported.
The SRA has carried out low-intensity attacks in the past, including blowing up train tracks, but its separatist fight has been less violent than that of neighbouring Balochistan province.
The group is designated as a terrorist organisation by the government of Pakistan.
The Rangers, a wing of the Pakistan army, have been deployed around Pakistan and played a prominent role in crackdowns on militants and criminals in Karachi.
Imran Ismail, the Sindh governor, condemned both the attacks and ordered authorities to find and arrest those who orchestrated them.
Sindh's Chief Minister Murad Ali Shah ordered an inquiry into Friday's violence, which came days after a bomb exploded at a crowded bazaar in the garrison city of Rawalpindi, killing at least one person and wounding 15.
Authorities say police have detained at least one person suspected of involvement in planting the bomb in that attack, but an investigation is still ongoing.