Another 28 people were wounded in the most severe attack on the Revolutionary Guards in recent years.
Iran's parliament speaker Ali Larijani said the US was implicated in the bomb attack.
Earlier, Iranian state television cited informed sources as saying Britain was directly involved the 'terrorist' attack.
State television suggested that a Sunni rebel group called Jundollah (God's soldiers), linked by some analysts to the Taliban in neighbouring Pakistan, was the likely suspect for the attack.
The Revolutionary Guards blamed 'foreign elements' linked to the United States for the killings, which underlined deepening instability in Iran's southeast bordering Pakistan and Afghanistan.
Tehran accuses the US of backing Jundollah to create instability in the country but Washington denies this.
The attack occurred in the morning at the gates of a conference hall in the city of Sarbaz in Sistan-Baluchestan.
The province is the scene of frequent clashes between security forces, Sunni rebels and drug traffickers.
The two high-ranking commanders were the deputy head of the Guards' ground forces, General Nourali Shoushtari, and the Guards' commander in Sistan-Baluchestan province, General Mohammadzadeh.
Mr Shoushtari was also a senior official of the Guard's elite Qods force.
State TV said several senior officers were also killed, but did not give additional names.
