Balochistan province, this evening, police officials said.
Earlier in the day, 13 people, including two children, were injured in a blast near a hospital in Satellite Town area of Quetta.
The bomb, attached to a bicycle left in the hospital's parking lot, was triggered by remote control. The injured were taken to the Civil Hospital, where doctors described the condition of two persons as critical.
Hours later, another bomb went off in the busy Saryab Road area of Quetta. Two policemen were injured and a car was damaged by the blast.
The bomb was fitted on a bicycle that was left near a police station.
There have been seven bomb attacks in Quetta since last evening, including one carried out by a suicide bomber who was trying to target the minority Shia Hazara community.
Six persons, including a paramilitary trooper, were killed and over 40 injured in four bomb attacks on Tuesday.
In Peshawar, four persons, including two women, were injured this morning when a bomb went off in the congested Sirki Gate area. A house was damaged by the blast.
At least two kilograms of explosives were used in the attack, police said.
The bomb was planted in front of the house of Pakistan People's Party leader Muhammad Tariq, police said.
In yet another incident, two bombs went off along a key road in Dera Ismail Khan district of Khyber-Pakhtunkhwa province though there were no casualties.
Israr Khan Gandapur, an independent candidate in next month's polls, had a narrow escape as his motorcade passed through the area shortly before the blasts.
At Larkana in southern Sindh province, about 20 feet of a gas pipeline were destroyed by a bomb blast.
Gas supply to several towns and cities were cut off after the attack though there were no reports of casualties.
No group claimed responsibility for any of the attacks on Wednesday.
On Tuesday, a suicide bomber detonated his explosives-laden truck in Quetta when he was stopped at a check post while driving towards Alamdar Road, a neighbourhood with a large Shia Hazara population.
Six persons, including a Frontier Corps personnel, were killed in the attack.
The banned Lashkar-e-Jhangvi claimed responsibility for the suicide attack.
LeJ spokesman Abubakar Siddiq telephoned reporters in Quetta and said his group had carried out the attack.
Four persons were killed and about 20 injured when a bomb went off near an election office of the Muttahida Qaumi Movement in Karachi last night.
Two persons were killed instantly while two others died in hospital this morning.
Pakistan has witnessed a spike in militant violence ahead of the May 11 general election.
The banned Tehrik-e-Taliban has threatened to target workers and rallies of the MQM, Awami National Party and Pakistan People's Party.
The MQM closed all its election offices to protest the attack in Karachi last night.
MQM chief Altaf Hussain criticised the caretaker government and the Election Commission for failing to improve the security situation.