TEHRAN: Iran was Friday probing twin suicide bombings in a crowded Shiite mosque which slaughtered 27 people in an attack a shadowy Sunni rebel group said was to avenge the execution of its militant leader.

Thursday night`s bombings, which reportedly targeted members of Iran`s elite defence force, the Revolutionary Guards, struck the Jamia mosque in southeastern Zahedan.

It drew condemnation from the European Union, the United Nations and US President Barack Obama.

The bombers detonated their payloads as worshippers were celebrating the birthday of Imam Hussein, grandson of the Muslim Prophet Mohammed, on a day also annually observed as the Guards` Day.

The attack "has left 27 people martyred and 270 wounded," Health Minister Marziah Vahid Dastjerdi told the Mehr news agency, adding that 11 of the wounded were in critical conditions.

Deputy Interior Minister Ali Abdollahi said members of the Guards were among the dead and wounded but gave no details.

Ali Mohammad Azad, the governor general of Sistan-Baluchestan, the province of which Zahedan is the capital, said Iran was "investigating who was behind the attack," which was claimed Friday by Sunni rebel group Jundallah (Soldiers of God) as revenge for the hanging of its veteran leader Abdolmalek Rigi.

Rigi was executed on June 20 after Iranian warplanes intercepted a flight from the United Arab Emirates to Kyrgyzstan and security forces seized him.

"Jundallah announces to the people of Baluchestan and Iran that tonight (Thursday) two of its sons, in an unmatched operation striking at the heart of the Guards who had gathered in a mosque in Zahedan to celebrate Guards Day, were able to send more than a hundred of the Guards to hell," the group said in a statement posted on its http://junbish.blogspot.com/ website.

Zahedan has been repeatedly hit by attacks blamed on Jundallah, which has been fighting for nearly a decade to secure rights for ethnic Sunni Baluchis who form a significant proportion of the population in the province.

The group said Thursday`s bombings were carried out by two of its members, Abdulbasit Rigi and Mohammad Rigi.

"In the first phase of the operation Abdulbasit Rigi blew himself up among tens of Guards," the statement said.

"After intelligence, security service and military personnel surrounded the area, Mohammad Rigi blew himself up, sending to hell tens of others.

"This operation is in response to the non-stop atrocities in Baluchestan by the regime, which thought that through the martyrdom of Abdolmalek (Rigi) the fight will end," the statement added.

Zahedan MP Hossein Ali Shahriari told the Fars news agency that one of the bombers was a man dressed as a woman.

On Friday, an angry Shahriari submitted his resignation to parliament, blaming Tehran for the poor security in the restive province, Mehr reported.

"The officials have failed to fulfill their minimum duty which is to provide security there... so I submit my resignation," Shahriari said.

Tehran says Jundallah receives backing from US and British intelligence services in its fight against Iran.

Condemnations of the attacks poured in.

"The murder of innocent civilians in their place of worship is an intolerable offense, and those who carried it out must be held accountable," said the US president.

"The United States stands with the families and loved ones of those killed and injured, and with the Iranian people, in the face of this injustice," Obama said.

EU foreign policy chief Catherine Ashton said the attacks were "cowardly" and unjustified.

UN Secretary General Ban Ki-moon blasted them, saying "this senseless act of terrorism at a place of worship makes it all the more reprehensible."

Television footage of the attacks showed blood and flesh splattered on walls of the mosque and several body parts scattered in and around the building.

The mosque was crowded with worshippers, among them members of the Revolutionary Guards, an elite military force formed shortly after the 1979 revolution to defend the purity of the country`s Islamic system.

Jundallah has carried out several such deadly attacks in the province, many of them targeting the Guards.

Last October it claimed a suicide bombing that killed at least 42 people, including seven Guards commanders, in the town of Pisheen in Sistan-Baluchestan which borders Afghanistan and Pakistan.

In July last year, Iran hanged 13 Jundallah members in a mass prison execution, terming them "enemies of God" after convicting them of a string of offences, including kidnapping foreigners.

BDST: 0948 HRS, 17 July 2010