Pakistani President Pervez Musharraf said Thursday there were problems with Pakistan's investigation into Benazir Bhutto's killing, and conceded uncertainty remained over the exact cause of the former prime minister's death. However, he denied accusations that the military or intelligence services were involved in the attack. Musharraf spoke a week after the opposition leader's assassination in a shooting and bomb attack as demands for an international investigation into the attack intensified. Many Bhutto supporters expressed doubt about the government conclusion that she had been killed when a bomb blast slammed her head against her vehicle. In an effort to blunt the criticism, he invited Scotland Yard investigators to aid Pakistan's probe and conceded investigators may have erred in giving a precise cause of death just a day after her killing.