Gen Shooshtari was deputy commander of the ground force
Several top commanders in Iran's elite Revolutionary Guards have been killed in a suicide bombing in the volatile south-east of the country.
Iranian state television said 31 people died in the attack, in the Pishin region of Sistan-Baluchistan, and more than 25 were injured.
Shia and Sunni tribal leaders were also killed. A Sunni resistance group, Jundullah, said they carried it out.
President Mahmoud Ahmadinejad said the criminals would be punished.
"The criminals will soon get the response for their anti-human crimes," Irna quoted him as saying.
May 2009 A bomb explodes at a mosque in the provincial capital Zahedan, killing 19 and injuring 60.
February 2007 Suspected militants killed 11, including Iranian Revolutionary Guards, in a bomb attack in the provincial capital Zahedan.
March 2006 Gunmen posing as police kill 22 people, many government employees, after closing the Zabol-Zahedan road.
A top Guards officer has also vowed to deliver a "crushing" response to those behind the attack, according to Agence France Presse.
Sistan-Baluchistan is mainly made up of the Baluchi ethnic group, who belong to the Sunni Muslim minority of Shia-ruled Iran.
Jundallah has previously been accused by Iran of terrorist activities in the province.
Parliament Speaker Ali Larijani said "US action" contributed to the attack - an accusation dismissed by the US.
According to state media, one or more suicide bombers targeted the group of Revolutionary Guards leaders who had arranged to meet with tribal leaders.
One report said there were two bombs - one inside the meeting and one aimed at a convoy of guards just arriving.
Jon Leyne, BBC Tehran correspondent
Jundallah, or Army of God, has been involved in a long-running insurgency in Sistan-Baluchistan.
Some experts believe they may have ties with the Taliban or al-Qaeda, operating in Pakistan and Afghanistan. That is disputed, and another possibility is that Jundallah maintains more informal links with ethnic Baluchis in the neighbouring countries.
Jundallah is also believed to have ties with drugs smugglers, who race across the border in heavily armed convoys, taking drugs on the lucrative smuggling route from Afghanistan through to Western Europe.
Diplomats on official visits to see progress in Iran's war on the drugs trade are always heavily guarded.
In May Iran hanged several members for a major attack on a mosque in the provincial capital Zahedan.
The brother of the group's leader, Abdolmalek Rigi, was due to be executed, but remains in prison for further questioning.
The deputy commander of the Guards' ground force, General Noor Ali Shooshtari, and the Guards' chief provincial commander, Rajab Ali Mohammadzadeh, were among at least six officers killed, state news agency reported.
Mr Larijani, speaking at an open session of parliament which was broadcast live on state radio, said: "We express our condolences for their martyrdom.
"The intention of the terrorists was definitely to disrupt security in Sistan-Baluchistan Province."
"We consider the recent terrorist attack to be the result of US action. This is a sign of America's animosity against our country," Mr Larijani said, quoted by AFP.
"Mr Obama has said he will extend his hand towards Iran, but with this terrorist action he has burned his hand," he said, referring to US President Barack Obama.
The US condemned the attack, with a state department spokesman adding: "Reports of alleged US involvement are completely false."
Earlier reports on Iranian TV quoted what it called "informed sources" as saying that Britain was directly involved.
A Foreign Office spokesman said: "The British government condemns the terrorist attack... and the sad loss of life which it caused."
The Iranian government has previously accused both countries of supporting the militants.
Officially the Islamic Revolution Guards Corps (IRGC), or Pasdaran
Formed after 1979 revolution
Loyal to clerics and counter to regular military
Estimated 125,000 troops
Includes ground forces, navy, air force, intelligence and special forces
Commander-in-chief: Mohammad Ali Jafari
Iran President Ahmadinejad is a former member
Sistan-Baluchistan province, which borders both Pakistan and Afghanistan, has long been affected by smuggling, drug trafficking, banditry and kidnapping.
Jundallah, also known as the Popular Resistance Movement of Iran, says it is fighting against the political and religious oppression of the country's Sunni minority.
In May, three men were executed for their role in a bombing of a mosque during evening prayers which killed at least 19 people in the south-east city of Zahedan in Sistan-Baluchistan.
The hangings came two days after the attack and the men were in custody on other charges at the time of the bombing.
Revolutionary Guards were among 11 people killed in an attack in 2007 in Zahedan.
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