Iranian leaders have blamed foreign foes for a suicide bombing by Sunni militants, masking their shock at an attack that killed 42 people and dented the prestige of the increasingly powerful Revolutionary Guards. Iranian leaders, already under international pressure over their nuclear policy and facing domestic discontent over a disputed June election, have sworn revenge for Sunday's attack, which they blamed on the United States, Britain and Pakistan. “It damages the Revolutionary Guards because people will ask: how can people who can't look after themselves take care of the country's security?” said London-based analyst Baqer Moin. Guards commander Mohammad Ali Jafari said on Monday Iran had documents indicating direct ties between Jundollah and US, British and, “unfortunately”, Pakistani spy agencies. “Behind this scene are the American and British intelligence apparatus, and there will have to be retaliatory measures to punish them,” the ISNA news agency quoted him as saying. The bombing, the deadliest in years, occurred in the poor and neglected southeastern province of Sistan-Baluchistan, a conduit for smugglers and drug traders near the Pakistan border. The deputy head of the Guards ground forces was among those killed in the blast, which state media said was claimed by the rebel Sunni Jundollah group, active locally since 2004-5. The Revolutionary Guards, set up after the 1979 revolution, have grown over the past 30 years into a potent force with military, political, social and economic interests. Its influence has expanded since hardline President Mahmoud Ahmadinejad was elected in 2005. The Guards and the Basij religious militia they control, led efforts to quell public protests after Ahmadinejad's disputed re-election in June. Feeble control A study published on Monday by the Norwegian Defence Research Establishment said Jundollah's existence highlighted precarious security and feeble government control in the region. “It also shows the limits to unity within the Republic itself. This deals a blow to the credentials of the revolution and the international revolutionary aspects of Khomeini's doctrine,” it said. Iran's harsh accusations – the pro-government Kayhan daily said Israel's Mossad spy agency was behind the attack – disguised consternation among the leadership, Moin argued. “They have to find a foreign perpetrator to excuse themselves.” The United States, Britain and Pakistan denied any hand in the bombing, which followed a blast that killed 25 people in a Shi'ite mosque in the provincial capital Zahedan in May. At least 18 people accused of involvement in that attack or jailed as suspected members of Jundollah were later hanged. “The great paradox is that Iran, which has been active in support of different movements outside her own territory after the revolution, is now faced with serious armed opposition within her own borders,” the Norwegian study said. Several analysts say Jundollah, believed to be motivated partly by Baloch nationalism and partly by an austere brand of Sunni militancy, has had links in the past with the Taleban and Pakistan's ISI intelligence service. Most say there is no evidence it is connected to Al-Qaeda, but suggest it may get help from other sympathizers. Covert backing? Moin did not discount Iran's claims that Jundollah received US backing as part of clandestine efforts to subvert Iran during former President George W. Bush's administration. Iran itself may have inadvertently aided Jundollah, according to Lieutenant General Hadi Khan, who was Afghanistan's deputy interior minister for security from 2006 to 2008. He told the Jamestown Foundation's Terrorism Monitor last month that Iran had at one point helped arm Taleban forces fighting US troops in neighboring Afghanistan. Iran denies supplying any weapons to the Taleban.