Abu Faraj al-Libbi, arrested 
                        in Pakistan this week, is a Libyan described by Pakistani 
                        officials as the key al-Qaeda operative in the country. 
                        But until a year ago, he was a relatively unknown figure 
                        in the hierarchy of alleged militants on the run since 
                        11 September. Libbi's name was first made public in Pakistan 
                        last year when it was included in the poster of six most-wanted 
                        militants issued by the government. Along with Amjad Farooqi 
                        - a man desperately wanted by Pakistani authorities for 
                        his alleged involvement in sectarian militancy inside 
                        the country - Libbi was advertised as a "terrorist" 
                        with 20m rupees ($340,000) offered for information leading 
                        to his arrest. 
                        
                        Breakthrough 
                        
                        Informed investigators working for the Pakistani military 
                        say Libbi, who suffers from the skin disorder, luecoderma, 
                        and used the alias Dr Tawfiq, had not initially been considered 
                        a major player in al-Qaeda by Pakistani authorities. It 
                        was only through the interrogation of a number of suspects 
                        - arrested between January and August last year - that 
                        the Pakistani authorities started taking note of his presence 
                        in the hierarchy, investigators say. One security official 
                        said: "Every time we interrogate a militant linked 
                        to al-Qaeda, al-Libbi's name pops up." 
                        
                        According to Pakistani investigators, the first breakthrough 
                        came with the arrest of Naeem Noor Khan in Lahore in July 
                        last year. 
                        Security officials say that Khan's interrogation revealed 
                        the extent of al-Qaeda operations in which Libbi and Farooqi 
                        were involved. 
                        
                        The two were learned to be actively communicating with 
                        al-Qaeda operatives outside Pakistan and in particular 
                        in the UK. The UK media ran several stories on Libbi's 
                        alleged plans to "carry out pre-election attacks 
                        in the US" for which he was said to be in touch with 
                        various UK-based agents through coded messages managed 
                        by Khan. 
                        
                         'Critical intelligence' 
                        
                        Libbi's exact standing in al-Qaeda remains unclear, but 
                        Pakistani and Western intelligence officials generally 
                        believe he took over as third in command of the organisation 
                        when his mentor, alleged 9/11 mastermind Khalid Sheikh 
                        Mohammed, was captured in March 2003. 
                        Farooqi was killed in a shootout with police in Nawabshah 
                        in central Sindh province in September 2005. 
                        
                        Security officials say Libbi has since been the main contact 
                        between al-Qaeda leader Osama Bin Laden and Islamic militants 
                        operating inside Pakistan. 
                        According to Pakistani security officials, the arrest 
                        last December of six militants from Karachi provided the 
                        authorities with some "critical intelligence" 
                        about Libbi's whereabouts. 
                        Libbi's arrest was preceded by a spate of speculation 
                        regarding "a major operation" in Pakistan's 
                        tribal belt of Waziristan - first hinted at by the head 
                        of US forces in Afghanistan, Lt Gen David Barno. 
                        
                        But irrespective of whether Libbi was specifically the 
                        focus, his arrest is still being described by Pakistani 
                        and Western officials as hugely significant. 
                        President Pervez Musharraf has directly blamed him for 
                        financing and supervising two attempts on his life in 
                        December 2003. 
                        
                        He is also regarded as the prime suspect in a number of 
                        bombing incidents in Pakistan, including last year's attempt 
                        to kill Prime Minister Shaukat Aziz. 
                        Libbi's arrest is also a significant indicator of the 
                        success of intelligence sharing between Pakistan and the 
                        US. 
                        
                        Islamists in Pakistan have repeatedly accused the Musharraf 
                        government of letting US agents operate on Pakistan soil. 
                        But Pakistan has consistently held that their cooperation 
                        with the Americans is limited to the sharing of information. 
                        
                        Pakistani security officials are now citing Libbi's arrest 
                        as a classic example of the success of this cooperation, 
                        whereby the US supplies Pakistan with the required intelligence 
                        and Pakistani forces carry out the actual operations.