A suicide car bombing on an Islamic Revolutionary Guard Corps bus in southeastern Iran killed 27 people on Wednesday, February 13, making it one of the deadliest attacks on the elite forces in years.

“The suicide attack on an Islamic Revolutionary Guards Corps personnel bus happened on the Khash-Zahedan road,” the official IRNA news agency reported right after the incident.

An “informed source” told the agency that “according to reports at least 20 have been martyred and 20 have been wounded.”

Later in the day, the Guards issued a statement with an updated death toll.

“In this terrorist attack 27 of Islam’s brave warriors were killed and 13 were wounded,” the statement read, accusing “world domination and Zionist intelligence agencies” of supporting the attackers.

#BREAKING: Suicide attack in SE #Iran kills 20, wounds another 20 Revolution Guards according to Fars News pic.twitter.com/vVleeOjXK5 — EHA News (@eha_news) February 13, 2019

The Guards said the troops were returning from the border, and the attack happened when “a car filled with explosives blew up besides a bus.”

“Mercenaries of intelligence agencies of world arrogance and domination,” carried out the attack to counteract “the victory of the 40th anniversary of the Islamic revolution,” they added.

Jihadist group Jaish al-Adl (Army of Justice) has claimed responsibility for the attack. Formed in 2012, the insurgent group was founded by members of the Sunni extremist group Jundallah (Soldiers of God) which has carried out a spate of attacks on Iranian security forces in recent years in the southeastern province of Sistan and Balochistan.

The attack on IRGC also took place in the province which has a large, mainly Sunni Muslim ethnic Baluchi community which straddles the border with Pakistan.

TRAC Incident Report: Jaish al-Adl (Army of Justice) Suicide VBIED (Truck Bomb) Targets Iranian Revolutionary Guard (#IRGC) Transportation Bus Chanali Area of Khash-Zahedan road, #Zahedan, Sistan-Balochistan Province, #Iran– 13 February 2019https://t.co/FvuSydSGVQ pic.twitter.com/dslFU3GWok — TRACterrorism.org (@TRACterrorism) February 13, 2019

On January 29, three members of an Iranian bomb squad sent to the scene of an explosion in Zahedan, the capital of Sistan Baluchistan province, were wounded when a second device blew up as they were trying to defuse it, police said at the time.

And in early December last year, two people were killed and around 40 others wounded in the port city of Chabahar, also in Sistan Baluchistan, in an attack which Foreign Minister Mohammad Javad Zarif at the time blamed on “foreign-backed terrorists.”

The bloodiest attack in recent times to have hit Iran took place in September when assailants killed 24 people at a military parade in the southwestern city of Ahvaz.

In July, at least 10 members of the Revolutionary Guards were killed when insurgents attacked one of their bases along the border with Iraq.

This story was updated throughout the day on February 13, 2019.

With reporting from AFP