Senior Al-Qaeda Yemeni operative arrested in Karachi, Pakistan.
Mohammed Ali Qasim, also known as Abu Suhaib al-Makki, had been working under al-Qaeda leaders along the Pakistan-Afghanistan border, a statement said.
The army said his arrest was a "major development in unravelling the al-Qaeda network operating in the region".
Officials later told the BBC that Qasim was key courier between Osama Bin Laden and his deputy, Ayman al-Zawahiri.
The BBC's Orla Guerin in Islamabad says that since Bin Laden was found and killed by US commandos on Pakistani soil on 2 May, the country's military establishment has been under scrutiny and pressure.
The US wants proof that Pakistan's army and powerful Inter-Services Intelligence (ISI) agency are not fighting militants with one hand, while helping them with the other, BBC reports.
Relations between U.S. and Pakistan have come to breaking point.