The US will face 'fallout' from a deadly rebel bomb attack in southeast Iran, a senior Revolutionary Guards commander was quoted as saying on Saturday by a semi-official Iranian news agency.

Massoud Jazayeri did not elaborate on what he meant. Iran has accused arch-foe Washington of backing Jundollah, the group that claimed responsibility for Thursday's blasts that killed 28 people and wounded 306, including members of the Guards.

'Jundollah has been supported by America for its terrorist acts in the past. America will have to await the fallout of such criminal and savage measures,' said Jazayeri, deputy head of the dominant ideological wing of Iran's armed forces.

Jundollah, a Sunni Muslim rebel group, said it set off the bombs at a prominent Shi'ite Muslim mosque in the city of Zahedan in retaliation for the Islamic Republic's execution in June of Jundollah leader Abdolmalek Rigi.

Iran says Jundollah has links to Sunni Islamist al Qaeda and in the past has accused Pakistan, Britain and the US of backing Jundollah to create instability in the southeast of predominantly Shi'ite Iran.

All three countries have denied this, and Jundollah denies having any association with al Qaeda.

Mohammad Hassan Rahimian, an envoy of Iranian Supreme Leader Ayatollah Ali Khamenei at the funeral, also blamed Washington for the attack, the official news agency IRNA reported.

US President Barack Obama on Friday condemned the bombing and said those responsible must be brought to account. 'The murder of innocent civilians in their place of worship is an intolerable offense, and those who carried it out must be held accountable,' Obama said in a statement.

The US is embroiled in a stand-off with Iran over its nuclear program, which Tehran insists is for peaceful energy purposes but Washington and other world powers suspect is a cover to develop the means to build atom bombs.

Tehran and Washington severed diplomatic relations shortly after Iran's 1979 Islamic Revolution.

Jundollah, which says it is fighting for the rights of Iran's Sunni Muslim minority, said Rigi's relatives carried out the bombings targeting a Revolutionary Guards gathering.

The bodies of those killed were buried on Saturday in a ceremony in Zahedan attended by tens of thousands of people, according to Iranian state television.

Live footage showed the coffins, shrouded in Iranian flags, being carried on trucks with mourners chanting 'Death to America' and demanding punishment of the attackers.

Iran arrested Rigi in February, four months after Jundollah claimed responsibility for a bombing which killed dozens of people, including 15 members of the Guards. That was the deadliest attack in Iran since the 1980s.

Zahedan is the capital of Sistan-Baluchestan province on the border with Sunni Muslim Pakistan. The province is dogged by serious security problems with frequent clashes between Iranian police and drug dealers and bandits.

A senior police official, Ahmadreza Radan, warned that Iran had a right to 'pursue rebels inside Pakistan territory. Iran has limited patience. Instability in Sistan-Baluchestan is rooted abroad (where) there is lack of will to confront rebels.'

He said 40 people 'who wanted to create instability' in Zahedan had been arrested there since the latest bombing.

Iran is grappling with ethnic and religious tensions in the southeastern province and authorities have responded to attacks by Sunni rebels with a spate of hangings. Human rights groups and the West have condemned the hangings.

Iran rejects allegations by rights groups that it discriminates against ethnic and religious minorities.-Reuters