Authorities first said the 11 were members of Iran's elite Revolutionary Guards, but then reversed course and identified them only as security officers. They were arrested after shooting out the tires of a car carrying smugglers, Pakistan authorities said.
The arrests could add to the strain between the two volatile nations triggered by the Oct. 18 attack on the Iranian side of the border. They came a day after the Pakistani president met Iran's interior minister and vowed to track down the perpetrators of the blast.
Pakistan has been accused of supporting militant activities in two other neighboring countries, Afghanistan and India, greatly complicating relations with both of them. Strains in its relationship with another regional power would only add to Pakistan's problems as it battles al-Qaida and the Taliban within its borders.
One Pakistani official later said three senior officers among the detainees probably belonged to Iran's powerful Revolutionary Guard.
Iran's Press TV carried what it described as a statement from the guard condemning the arrests, but saying that the 11 were not its members. The report cited "informed" sources as saying the arrested men were "border guards hunting fuel smugglers (who) accidentally entered Pakistan."
In an attempt to boost security in the region, Iran put the Revolutionary Guard directly in control of Sistan-Baluchistan province in April. Its officers typically take the lead in any operations on Iran's border.
The 11 officers were taken into custody in Mashkel district, about seven kilometers (four miles) from the countries' border in the southwestern Pakistani province of Baluchistan, paramilitary official Mohammad Naseer Baluch said.
He said they were arrested soon after they shot out the tires of a car driven by "two petty smugglers."
The Oct. 18 suicide attack killed 15 members of the Revolutionary Guard, including five senior commanders, and at least 27 others in the town of Pishin.