FACTBOX: Bhutto assassination investigation and controversy

(Reuters) - Two Pakistani inquiries are investigating the assassination of opposition leader Benazir Bhutto.

Following are the main points of controversy in her death:

WHO ORDERED THE ATTACK?

* The government says Baitullah Mehsud, a Pakistani militant linked to al Qaeda, ordered the assassination. A spokesman for Mehsud, who is based on the Afghan border, denied involvement.

* Bhutto's Pakistan People's Party rejects the government's version. It says the authorities are trying to cover up their failure to provide security, and suggests that she was killed by other, unidentified enemies.

WHO CARRIED OUT THE ATTACK?

* Investigators have reconstructed a mangled head, apparently that of the bomber, found at the scene of the attack along with severed fingers. DNA tests are being done to see if they belong to the same person.

* Pakistan's Dawn News Television has broadcast grainy still pictures of what it said appeared to be two attackers.

One is a clean-cut young man wearing sunglasses, white shirt and dark waistcoat. Behind him stands a man with a white shawl over his head, who Dawn said was believed to be the bomber. Two photographs show the clean-cut man pointing a pistol at Bhutto.

Officials have declined to say how many attackers they think were involved.

HOW DID BHUTTO DIE?

* The government says three shots were fired at Bhutto as she left an election rally in the city of Rawalpindi. But, citing a medical report, it says she was killed when a blast set off moments later by a suicide bomber smashed her head into a lever on the sunroof of her bullet-proof vehicle as she ducked down.

* The PPP says this is "ludicrous", and that she was killed by a bullet to the head.

WHO IS INVESTIGATING?

* The government has ordered two separate investigations -- one by police and security services, and one by the judiciary.

* Bhutto's husband, Asif Ali Zardari, who was appointed co-chairman of her party on Sunday, said the party wanted the United Nations to investigate.

(Writing by Robert Birsel, Editing by Kevin Liffey)