The helicopter that crashed killing the Iranian president, Ebrahim Raisi, and the foreign minister, Hossein Amir-Abdollahian, either did not have a transponder fitted or had it turned off, according to an initial investigation by the Turkish rescue group that found the wreckage. The Turkish transport minister, Abdulkadir Uraloğlu, told reporters that on hearing news of the crash, Turkish authorities had checked for a signal from the helicopter’s transponder that broadcasts height and location information. “But unfortunately, [we think] most likely the transponder system was turned off or that the helicopter did not have one,” he said. It also emerged that the Iranian government had been urged in a memo by officials to purchase two Russian helicopters for its leaders amid concerns over the maintenance of its fleet of ageing helicopters. The former foreign affairs minister Mohammad Javad Zarif blamed US sanctions for making it difficult to purchase spares for the fleet, adding that the crash would be “recorded in the blacklist of American crimes against the Iranian nation”. The helicopter involved in the crash was a Bell 212, a two-blade aircraft capable of carrying 15 people. An investigation team has already arrived at the site of the crash in the province of East Azerbaijan, and will also be examining if weather checks were made before the decision to fly was taken. The two other helicopters in the group completed the journey safely, and so far there has been no serious allegation of sabotage. Five days of mourning have been announced, with the president’s funeral to be held on Wednesday, when officials said the whole country would be closed. An election for his successor is expected at the end of June, probably 21 June. The helicopter crashed on Sunday morning in thick fog in a remote mountainous part of northern Iran, the conditions hampering a rescue effort that was unlikely to have saved lives even if the Red Crescent crews had been able to reach the victims more quickly. The charred bodies were only revealed by a Turkish government surveillance drone after the fog lifted and the sun rose on Monday morning. State media reported that the aircraft had “hit the mountain and disintegrated” on impact, leaving “no signs of life”. The crash happened as Raisi and his entourage were on their way back from the province, where he had been attending the opening of the Giz Galasi hydroelectric complex, a joint project of Iran and Azerbaijan on the Aras border river. The crash killed all nine occupants of the helicopter, leaving a leadership vacuum that hardliners will now rush to fill before elections for a new president are held within 50 days. A provisional timetable has been set culminating in a late June election. The Russian leader, Vladimir Putin, praised Raisi as an “outstanding politician”, saying his death was an “irreplaceable loss”. Iranian-made Shahed kamikaze drones have been critical in helping Russian to hit civilian and military installations in Ukraine. The supreme leader of Iran, Ayatollah Ali Khamenei, also praised Raisi, saying that Iran had lost “a sincere and valuable servant”. Politicians opposed to the Iranian regime, including the EU foreign affairs chief Josep Borrell, expressed their condolences at Raisi’s death – but even this humanitarian gesture angered Iranian opponents of the repressive regime. Britain’s security minister, Tom Tugendhat, was an exception, sending out a message on X: “President Raisi’s regime has murdered thousands at home, and targeted people here in Britain and across Europe. I will not mourn him.” The Iranian poet laureate Shirin Ebadi said: “The people of Iran had hoped to see him brought to justice, to witness how he would struggle and plead for his own exoneration. He did not deserve such an easy death.” Raisi was largely seen as unimpeachably loyal to the 85-year-old supreme leader, and his death presents the regime with a task of hurriedly selecting a candidate to win the presidential elections now scheduled for within two months – and a more medium-term challenge of deciding on an alternative to Raisi as a successor to the supreme leader. Raisi, 63, was widely seen as a leading candidate, but others, including Khamenei’s son Mojtaba Khamenei , have been mentioned. Dr Afshin Shahi, a senior lecturer in Middle East politics at Keele University, said: “Under Raisi’s leadership, the Islamic Republic faced the worst legitimacy crisis in its history. Despite severe crackdowns on the ‘Women, Life, Freedom’ movement, most people considered Raisi an irrelevant figure, directing their anti-regime slogans at the supreme leader and IRGC [Islamic Revolutionary Guard Corps] instead. During his tenure, measures were intensified to securitise society, granting the IRGC an even more prominent role. “With reformists almost entirely excluded from power, Raisi’s tenure has witnessed unprecedented factionalism and antagonism among hardliners. Although the IRGC and the supreme leader will engineer the upcoming presidential election in 50 days, internal conflicts among hardliners – who are openly fighting for more power and resources – might influence the outcome.” Raisi, backed by a group that wanted to see him become supreme leader, had clearly wanted the role, said Vali Nasr, a professor of Middle East studies at Johns Hopkins School of Advanced International Studies. “Now they don’t have a candidate, and that opens the door for other factions or other figures to emerge as serious contenders,” he said. Mohammad Mokhber, Iran’s vice-president, charged under the Iranian constitution with running the country pending the fresh presidential elections, has also been put in charge of the arrangements for Raisi’s funeral. Ali Bagheri, a diplomat who played a key role in the unsuccessful Vienna talks to restart the 2015 nuclear deal, was appointed acting minister of foreign affairs. With some anti-regime groups openly celebrating Raisi’s demise, Mohammad Movahedi Azad, the attorney general, called on prosecutors to take “quick, effective and deterrent action … against the people who by publishing information about the killing of a president attempt to disturb the psychological security of the society and disturb the public mind”.