Pakistan security forces have arrested a senior al-Qaeda official in Karachi on Tuesday, suggesting that Islamabad may finally get serious about cracking down on terrorists operating within her borders, two weeks after the spectacular killing of Osama bin Laden by US commando forces.

The detained man is named Muhammad Ali Qasim Yaqub (alias Abu Suhaib al-Makki) a Yemeni national who is believed to have worked directly with al-Qaeda operatives on the lawless Pakistan-Afghanistan border.

Pakistan army officials described the arrest as a major development in unraveling the al-Qaida network operating in the region.”

Since the discovery of bin Laden in a compound in northern Pakistan, U.S. officials have pressured Islamabad to go on an offensive against militants. During a personal visit, US Senator John Kerry carried this message directly to Prime Minister Yousuf Raza Gilani.

“This relationship [between the U.S. and Pakistan] will not be measured by words or by communiqués after meetings like the ones that I engaged in. It will only be measured by actions,” Kerry warned.

With bin Laden’s demise, the two most wanted terrorists (both of whom are believed to be living somewhere in Pakistan) are Ayman al-Zawahiri, the second man in al-Qaeda; and Mullah Omar, the boss of the Taliban.

Pakistan is also under pressure to capture and prosecute leading members of the home-grown Lashkar-e-Taiba, which are blamed for the 2008 massacre in Mumbai, India, which killed more than 170 people.

US officials are currently trawling through a massive trove of intelligence materials seized during the commando raid at Abbottabad that killed bin Laden. It is unclear whether or not the apprehension of Makki was a result from the intelligence.