The Iranian authorities blame Obama, America and Britain for the attack.
BBCNEWS…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 Ahmandinejad said the criminals would be punished.
“The criminals will soon get the response for their anti-human crimes,” Irna quoted him as saying.
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.
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.
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.