Iranian commanders assassinated
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 interior ministry said 29 people died in the attack, in the Pishin region of Sistan-Baluchistan, and at least 28 were injured.
Shia and Sunni tribal leaders, who gathered for a meeting with the guards, were among the dead.
Parliament Speaker Ali Larijani said "US action" contributed to the attack.
Iran has previously accused a Sunni resistance group, Jundallah, of terrorist activities in the province.
Sistan-Baluchistan is mainly made up of the Baluchi ethnic group, who belong to the Sunni Muslim minority of Shia-ruled Iran.
"Very soon we will catch the perpetrators of this terrorist action and punish them," a statement on the interior ministry's website said, according to AFP news agency.
One report said there were two bombs - one inside the meeting and one aimed at a convoy of guards just arriving.
'Terrorist' attack
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.
Earlier reports on Iranian TV quoted what it called "informed sources" as saying that Britain was directly involved.
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.
