The twin explosions occurred in Karachi near the motorcade of Bhutto, who returned to Pakistan Thursday after eight years of self-imposed exile, CNN reported. Thousands of people turned out for her return.
Ashraf Jehangir Qazi, Pakistan's ambassador to the United States, expressed sorrow about the loss of life, but added "the good news is Benazir is safe and sound."
"(This) was a very joyous occasion," the ambassador told CNN, "but such an attack was a possibility."
Witnesses said dozens of people were dead and hundreds were injured. A CNN reporter said he counted at least 10 bodies, adding he saw "more bodies than I can count."
Police recovered the body of "what they say is a suicide bomber," CNN reported.
Bhutto's convoy was snaking through a sea of people in Karachi when the explosions occurred.