The official IRNA news agency said the dead included the deputy commander of the Guard's ground force, Gen. Noor Ali Shooshtari, as well as a chief provincial Guard commander for the area, Rajab Ali Mohammadzadeh. The other dead were Guard members or local tribal leaders. More than two dozen others were wounded, state radio reported.
The headquarters of Iran's armed forces blamed the bombing on "terrorists" backed by "the Great Satan America and its ally Britain," Fars News Agency was quoted by Reuters.
"Not in the distant future we will take revenge," Iran's statement read, according to Reuters. Iran's forces claim the country "will clear this region from terrorists and criminals."
"The global arrogance, with the provocation of its local mercenaries, targeted the meeting of the Guard with local tribal leaders," said the Guard statement read out on state TV.
The United States, however, condemned the attacks on Sunday and denied any involvement.
"We condemn this act of terrorism and mourn the loss of innocent lives. Reports of alleged U.S. involvement are completely false," U.S. State Department spokesman Ian Kelly said in a brief statement.
The Revoutionary Guard commanders were inside a car on their way to a meeting with local tribal leaders in the Pishin district near Iran's border with Pakistan when an attacker with explosives blew himself up, IRNA said.
Iran's state-owned English language TV channel, Press TV, said there were two simultaneous explosions: one at the meeting and another targeting an additional convoy of Guards on their way to the gathering.
There was no immediate claim of responsibility, but the region in Iran's southeast has been the focus of violent attacks by a militant group from Iran's Sunni Muslim minority called Jundallah, or Soldiers of God, which has waged a low-level insurgency in recent years.