The motive for the killings and the number of those killed is unclear, but the deaths could make peace between Afghanistan's government and the rebels more elusive as Western troops prepare to leave the war-torn nation.
Afghan officials say several of the victims had been discussing unauthorised peace talks with the government in Kabul.
Officially, the Taliban has denied any such spate of deaths.
"Now the enemy is facing defeat they have turned to baseless propaganda and they call anyone who gets killed a member of the Taliban council or Mullah Mohammad Omar's close confidante," a Taliban statement said on Friday, referring to the movement's reclusive one-eyed leader.
However, four members of the Afghan Taliban told Reuters last week that the insurgency had killed some of its own commanders because the men were involved in unauthorised talks.
One Quetta-based commander put the figure of such deaths at 18 since the beginning of last year.
Quetta is about 80 km (50 miles) from the Afghanistan border and used to be a popular winter refuge during the hey days of the Taliban government in Afghanistan. Afghan officials have long accused Pakistan of supporting the insurgents and giving them sanctuary, a charge which Islamabad denies.
Both the Taliban and Quetta police say that gunmen shot Noorullah Hottak two weeks ago.
Afghan security officials had claimed that Hotak was an active Taliban commander, a member of alleged Quetta ‘Shura’.
But the official Taliban statement acknowledging his death denied that, calling him a "former" warrior.
Last month, gunmen killed Mullah Abdul Malek, another Taliban figure, said a Quetta-based Taliban commander and an Afghan intelligence official.
The Taliban denied his death, and the deaths of two other commanders, in their statement.
"These commanders are alive and busy with their jihad (holy war) tasks," said the statement.
Around a dozen Taliban members of varying ranks were killed in Quetta in last year's winter, said Rahmatullah Nabil, the head of Afghanistan's intelligence service.
Nabil said he had investigated the killings and the victims had all sought unauthorised peace talks.
"All 12 had been speaking to the president's negotiators, either directly or through provincial governors or tribal elders," he said.
Blaming Pakistan
Since the killings started up again last month, a senior Afghan official blamed the killings on Pakistani officials, saying they feared losing influence over commanders who had started peace talks.
"Pakistan thinks if we're making progress with these (Taliban leaders), that might break their hold on them," claimed the official, who asked not to be named.
Pakistani officials say they have no idea who is behind the killings.
"Pakistan has been making all possible efforts to facilitate a reconciliation process in Afghanistan," said a Pakistani security official who asked not to be named.
A Taliban commander in Quetta blamed the killings on Afghan intelligence, saying they were targeting senior members of the rebel group.
But all sides have a reason to lie about who is behind the killings, said Saifullah Mehsud of the Islamabad-based thinktank, the FATA Research Center.
"Many are in the drug trade, others are arms smugglers. It could be a matter of revenge. It's not clear who killed them or why," he said.
COMMENTS (5)
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Drone please.
I assure you the Afghans are fed up too. Why are these people operating freely in Quetta? Maybe thats the question you should be asking.
@Zog @Zif Why in heavens name stop now to do anything we live in cowardly nation that is totally incapable from protecting its citizens from any harm local or foreign. We moan & groan & blame the WEST to hide our inadequate capacity to protect ourselves!
Fed up and tired of this Afghanistan affair. We want peace and our lives back!
Can we please repatriate these folks legally / humanely to their country... They have destroyed the soccial, economic and environmental fabric of Pakistan No other country would tolerate such abuse of their laws