Mullah Hakim Latifi was caught in southwestern Baluchistan province, Information Minister Sheikh Rashid Ahmed said. Baluchistan borders Afghanistan, and members of the Taliban are believed to have sought refuge in the area after Afghanistan's ruling militia was ousted in a US-led invasion in 2001.
"It is a big success. We were looking for him for a long time," Ahmed said.
Ahmed said Pakistan had not made any decision to hand over the Taliban spokesman to Kabul.
"It is premature to talk about it. First our security agencies will question him," he said.
Interior Minister Aftab Khan Sherpao confirmed the arrest. Another interior ministry official said Latifi had been using a Pakistani mobile phone and would be moved to Islamabad, the Pakistani capital, for questioning.
"He was tracked down on a tip in a Pakistani town," the official said on condition of anonymity because he is not authorized to speak to media. He said some associates of Latifi were also captured, but did not identify them.
Sherpao described Latifi as the Taliban's chief spokesman. But information from Hakimi in the past has sometimes proven exaggerated or untrue. Afghan and US military officials say he is believed to speak for factions of the rebel group, though his exact ties to the Taliban leadership cannot be verified.
Latifi was not a prominent figure in the Taliban while the Islamic militia was in power, only becoming a media contact after the ouster of the movement.
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The arrest came less than a week after Afghan President Hamid Karzai praised Pakistan for helping Afghanistan hold peaceful legislative elections on September 18. Pakistan had deployed additional troops to prevent Taliban and al-Qaida fighters from operating along the border as part of a campaign to disrupt the election.
Relations between Pakistan and Afghanistan have sometimes been strained because of Afghan suspicions that rebels are using Pakistan as a staging area for cross-border attacks. Pakistan denies it.
Rebels are active in the volatile south and east of Afghanistan, and have stepped up attacks this year. More than 1,300 people, including hundreds of militants, have died in the past seven months.
Pakistan was once a supporter of the Taliban, but withdrew its support and became a chief ally of the US-led coalition forces that ousted the militia.
On Tuesday, a panel composed of senior military and diplomatic representatives from Afghanistan, Pakistan and US-led coalition forces in Afghanistan met near the Pakistani capital to discuss how to counter insurgents.
"All parties further agreed that continued cooperation and coordination to enhance security was essential to long-term success against al-Qaida and terrorist movements," the US military said in a statement.