Three al-Qa'ida members including a top operative believed to have been tasked by Osama bin Laden with targeting American economic interests around the world have been held in Pakistan.
Younis al-Mauritani's arrest five days before the 10-year anniversary of the 9/11 attacks was seen as a blow to al-Qa'ida's central leadership in Pakistan, further degrading its ability to mount terrorist attacks abroad.
The terrorist organisation has seen its senior ranks thinned since Osama bin Laden was killed in May then Atiyah Abd al-Rahman, the group's No.2, in a CIA missile strike last month.
The Pakistani military said the arrests, with CIA co-operation, took place near the Afghan border in the south-western city of Quetta, long known as a base for militants.
The capture of an al-Qa'ida militant inside Pakistan has become rare in recent years: most targets of CIA operations in the country have been killed by drone aircraft in a relentless series of operations launched in 2008.
"This operation was planned and conducted with technical assistance of United State Intelligence Agencies with whom Inter-Services Intelligence has a strong, historic intelligence relationship. Both Pakistan and United States Intelligence agencies continue to work closely together to enhance security of their respective nations," the military said.
It said al-Mauritani was mainly responsible for al-Qa'ida's international operations and was tasked by bin Laden with hitting targets of economic importance in America, Europe and Australia. It said he was planning to target US economic interests including gas and oil pipelines, power generating dams and oil tankers by using explosive-laden speed boats in international waters.
It named the other two detainees as Abdul-Ghaffar al-Shami and Messara al-Shami.
Since the 2001, attacks, Pakistan's spy agency has co-operated with the CIA to arrest scores of al-Qa'ida suspects, most of whom were handed over to the United States.
Many top al-Qa'ida commanders are still believed to live in Pakistan, and getting Islamabad's co-operation in cracking down on the network has been a top American goal since 2001. But there have been persistent suspicions that the country was protecting militants. The fact that bin Laden was killed in an army town close to the capital, Islamabad, led to fresh doubts over Pakistan's commitment.