TEHRAN - A suicide bomber killed six senior Revolutionary Guards commanders and 23 other people on Sunday in one of the boldest attacks on Iran's most powerful military institution.

The attack, in the country's turbulent southeast, came as Iranian officials were to meet Western counterparts for a second round of negotiations in Vienna on Monday intended to help resolve a standoff with the West about Iran's nuclear ambitions.

State media said a local rebel group called Jundollah (God's soldiers) claimed responsibility for the attack, the deadliest on the elite Revolutionary Guards in recent years, which also wounded another 28 people at a meeting of tribal chiefs.

Rigi's terrorist group has claimed responsibility for the attack, said state television, referring to Abdolmalek Rigi, leader of Jundollah which is linked by some analysts to the Taliban in neighboring Pakistan.

The Guards themselves accused foreign elements linked to the United States of involvement. Tehran accuses the United States of backing Jundollah to create instability in the country, a charge that Washington denies.

State television also pointed the finger at Britain, another traditional foe of Iran.

The Revolutionary Guards is an elite force seen as fiercely loyal to Iran's Supreme Leader, Ayatollah Ali Khamenei. Its power and resources have increased in recent years. It handles security in sensitive border areas.

FOREIGN ELEMENTS

The bombing and allegations of foreign involvement risk overshadowing the nuclear talks in Vienna, between Iranian, U.S., French and Russian officials.

The attack is also likely to harden the resolve of the clerical and military establishment in confronting the opposition to a disputed election in the summer which saw the re-election of President Mahmoud Ahmadinejad.

Iranian opposition leader Mirhossein Mousavi said he would press ahead with efforts to reform the Islamic Republic despite a crackdown on protests after the June 12 presidential poll, his website said on Sunday.

The election plunged Iran into its deepest internal crisis since the 1979 Islamic revolution. The opposition says more than 70 people were killed as Revolutionary Guards and Islamic militia put down the protests that erupted after the poll.

Citing a witness, state television said Sunday's attack occurred when senior Revolutionary Guards officers attending a conference in the southeastern city of Sarbaz went to talk to a group of tribes people making baskets.

English-language Press TV said the suicide bomber was one of the tribesmen who detonated his explosives strapped to his body.

Among those killed were the deputy head of the Guards' ground forces, General Nourali Shoushtari, and the Guards' commander in Sistan-Baluchestan province, General Rajabali Mohammadzadeh, Iranian media reported. Shoushtari was also a senior official of the Guards' elite Qods force.

General Shoushtari, along with a number of other (Guards) commanders, had gone there to attend a conference, Press TV quoted a witness as saying.

But before going there, there were some tribes people who were busy basket-making, and they went to talk to them and that's when the attack happened, said the witness, a man it named as Morteza Etasi.

General Shoushtari got killed along with a number of other along with a number of other senior (Guards) commanders and tribes people.

The southeastern province is the scene of frequent clashes between security forces, Sunni rebels and drug traffickers.

Citing authorities and experts, a presenter of English-language Press TV said the finger of accusation is directly pointed at the Jundollah group, referring to ethnic Baluch Sunni insurgents who have been blamed for previous attacks in the region.

Jundollah, which claimed responsibility for the bombing of a Shi'ite mosque in May that killed 25 people, says it is fighting for the rights of the Islamic Republic's minority Sunnis.

Some analysts believe that Jundollah has evolved through shifting alliances with various parties, including the Taliban and Pakistan's ISI intelligence service, who saw the group as a tool against Iran.

Predominantly Shi'ite Muslim Iran has also linked Jundollah to the Sunni Islamist al Qaeda network. Most people in Sistan-Baluchestan are Sunni Muslims and ethnic Baluchis. Iran rejects allegations by Western rights groups that it discriminates against ethnic and religious minorities.

(Reporting by Fredrik Dahl and Reza Derakhshi; Additional reporting by Parisa Hafezi in Tehran and Peter Griffiths in London; Writing by Samia Nakhoul; Editing by Jon Boyle)

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