The Revolutionary Guards branch in south-eastern Iran said in a statement that a unit of its ground forces had been returning from the Pakistan border area on Wednesday when a vehicle filled with explosives blew up beside their bus.
The attack happened on the road between Khash and Zahedan, in the volatile province of Sistan-Balochestan, at the border between Iran, Afghanistan and Pakistan.
The terrorist group has claimed in their post on their telegram channel that all the 40 IRGC personnel have been killed in the attack.
Twelve members of the Guards were among 25 people killed last autumn by gunmen on a military parade in the city of Ahvaz in the southwest. Thirteen people were wounded.
Tehran immediately linked the attack in Iran's restive southeastern Sistan and Baluchistan province to an ongoing US -led conference in Warsaw largely focused on Iran, just two days after the nation marked the 40th anniversary of its 1979 Islamic Revolution.
Iranian foreign ministry spokesperson Bahram Qassemi vowed retaliation for Wednesday's attack. While Jaish al Adl and other groups like it are not regarded as a major security threat, the attack is a fresh blow to the image of the Guards, the most powerful force in Iran, which reports directly to Supreme Leader Ayatollah Ali Khamenei. In 2018, the Guards launched missiles at an Iranian Kurdish armed opposition group in northern Iraq.More news: IEA Says Venezuela Crisis Risks Disrupting Global Crude Market
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Jaish al-Adl claimed Wednesday's bombing in a statement online.
Iranian officials have blamed Saudi Arabia and the United States for stirring up dissent in the country.
In a tweet, Iranian Foreign Affairs Minister Javad Zarif, who has been critical of the Warsaw gathering, obliquely implied there could be a connection between the summit and the attack on the Revolutionary Guards. Since then, the United Nations says Iran has kept up its side of the bargain, though Iranian officials have increasingly threatened to resume higher enrichment.
"Is it no coincidence that Iran is hit by terror on the very day that #WarsawCircus begins?"
The group, which is based in Pakistan, opposes the government in Tehran and has in the past carried out successful attacks against Iranian troops, including kidnappings, and an April 2017 ambush on the Pakistan border that killed nine border guards.