Pakistan's military said on Saturday it had no information on a US media report that al Qaeda's deputy leader Ayman al-Zawahiri may have been wounded or killed in a missile strike.
  
US television channel CBS said it had obtained an intercepted letter from a Pakistani Taliban commander urgently requesting a doctor to treat Zawahiri following the attack in a tribal area bordering Afghanistan last week.
  
"There is no evidence or information in this regard. We have no reliable information," chief Pakistani military spokesman Major General Athar Abbas told AFP.
  
Pakistani officials have previously said that a July 28 missile strike in the South Waziristan tribal area killed al Qaeda's top chemical and biological weapons expert, Midhat Mursi al-Sayid Umar.
  
A senior military official based in northwestern Pakistan said he was checking the CBS report that Zawahiri, an Egyptian militant and number two to Osama bin Laden, was also hit.
  
"We have seen the media report that al-Zawahiri was killed or wounded in the July 28 strike. We are investigating the authenticity of the report," the official said on condition of anonymity.
  
The official said authorities were also trying to obtain the letter, which CBS said was written by Pakistani Taliban leader Baitullah Mehsud.
  
An intelligence official based in South Waziristan said they had heard rumours about Zawahiri being targeted a few days ago "and we checked it but we have not been able to confirm it."
  
A spokesman for Mehsud was not immediately available.
  
CBS said the letter from Mehsud dated July 29 carried his seal and signature, refers to Zawahiri by name and says the Egyptian is in "severe pain" and his "injuries are infected."
  
A US-based terrorism monitoring group, IntelCenter, said on Friday that it "is aware of and has been monitoring for a few days now reports that al Qaeda's Ayman al-Zawahiri has been killed or severely injured in the strike."
  
It said that if Zawahiri was dead, al Qaeda would be expected to release the news "with a fair amount of speed either in a video and/or written statement."