The nature of the blast has yet to be ascertained.
Sarfraz Bhugti, Home Minister of Balochistan, said the attack happened when a suicide bomber rammed his explosive-laden vehicle into the security forces truck in Saryab area of Quetta, killing seven people on the spot and wounding 22 others.
Police and FC troops have reached the area, which has been cordoned off for gathering evidence.
The Pakistani Taliban claimed responsibility for the auto bombing, which took place in the Saryab Road area of Quetta, the provincial capital of Baluchistan.
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The minister said that 21 others were injured in the attack on Sariab Road near Darakhshan Railway Phaatak, while a police official put the number of wounded at 25.
"We can not yet say that this is a suicide attack, our teams are in research and investigations at scene", Cheema said.
Quetta's deputy police inspector general, Razzaq Cheema, explained that before the attack they had information about plans by extremist groups.
Home Minister Bugti, while condemning the attack, said the war against terrorism was not over and would go on until no terrorist remained in the area.
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"We are at war and our security forces are being targeted as they are crushing the enemies", Bugti said. According to initial reports, Abdul Salam was shot multiple times in what was reported as a targeted killing. On August 13 this year, at least 15 people, including eight soldiers, were martyred when a military truck was targeted in Quetta.
Earlier in June, 14 people - including seven policemen - lost their lives in a suicide blast that shook Shuhada Chowk in Quetta's Gulistan Road area.
Prime Minister Shahid Khaqan Abbasi also strongly condemned the terrorist attack in Quetta and directed authorities to provide best possible medical treatment to the injured.
Pakistani leaders, including Imran Khan, and members of the civil society condemned the attack, praying for the victims.
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Sources in the Pakistan Cricket Board, however, claimed that the SLC will try and convince the players to tour Lahore . The victory gives Pakistan a 2-0 lead in the five-match series while this becomes Sri Lanka's ninth defeat in a row.