Yemeni al Qaeda operative Abu Sohaib Al-Makki, arrested by Pakistani security agencies was a "key courier" between slain terror mastermind Osama bin Laden and his deputy Aiman al-Zawahiri.
Muhammad Ali Qasim Yaqub alias Abu Sohaib Al-Makki, described as a "senior al Qaeda operative", was arrested by security agencies in Karachi, the military announced on Tuesday.
Yaqub was one of the main couriers between bin Laden, who was killed in a US raid in Abbottabad on May 2, and al-Zawahiri, unnamed security officials told BBC.
He was arrested in Karachi's central Gulshan-e-Iqbal area on May 4.
He had a satellite phone and a tracking device, which had yielded new information about al Qaeda's activities in the region, the officials said.
He is also said to have been an important recruiter, which led to him travelling abroad frequently.
Yaqub moved around Pakistan to avoid detection, living in Abbottabad, Faisalabad, Peshawar and Karachi.
He was involved in planning attacks on Saudi interests in Pakistan and had ordered retaliatory strikes following bin Laden's death, the officials said.
It could not immediately be ascertained if these retaliatory attacks included the killing of Saudi diplomat Hassan al-Kahtani in Karachi on Monday.
The Pakistani military's statement said Yaqub worked directly under al Qaeda's leaders along the Pakistan-Afghanistan border.
His arrest was a "major development in unravelling the al-Qaeda network operating in the region", the military said.
Diplomatic sources said it was too early to conclude that Pakistani authorities had initiated a crackdown on al Qaeda in the wake of the killing of bin Laden, an event that embarrassed and humiliated the powerful Pakistan Army and Inter-Services Intelligence agency.
Some observers noted that Pakistani security agencies had launched a "crackdown" on the Jamaat-ud-Dawah in the wake of the 2008 Mumbai attacks and sealed dozens of offices and detained over 100 activists and leaders.
Within months, most of the activists were freed and the offices too were subsequently reopened.
Yaqub's arrest was announced just a day after US Senator John Kerry said Pakistan needed to flush out terrorists from its soil and crack down on terrorist sanctuaries in the tribal areas.
The al-Qaeda operative, believed to be about 40 years old, had reportedly been living in Karachi with his wife and three children for some time.