Twenty members of the Iranian Revolutionary Guard were killed in a suicide attack Wednesday in the southeast of the country.
At least ten members of the Guards were also injured in the suicide bombing bomb attack involving a bus carrying security forces, Fars reports in Iran.
The state-run news agency IRNA, citing an "informed source," reported that the security forces in the Iranian province of Sistan-Baluchestan were being attacked.
"This terrorist act has recently taken place and reportedly at least 20 martyrs were killed," IRNA quoted the source.
In the province, which is on an important route of the opium trade, clashes occasionally occurred between Iranian forces and Baluch separatists and drug traffickers.
The attack took place on the road between the cities of Zahedan and Khash, a volatile area near the Pakistani border, where armed groups and drug smugglers often operate.
The armed group of Jaish al-Adl took responsibility for the attack, according to Fars.
A photo published by the news agency showed a pile of twisted metal at the scene.
The Guard made a statement confirming the attack. The troops returned from the border.
"In this suicide bombing, a car filled with explosives blew up next to a bus carrying a unit of the Guard's ground forces, causing martyrdom and a string of protectors on the border of our Islamic homeland."
The attack came on the day of a US-led conference in Warsaw, during which discussions took place about what the United States calls Iran's "evil influence" throughout the Middle East.
The Iranian authorities have blamed Saudi Arabia and the United States for provoking dissent in this country.
The Guard is an important economic and military power in Iran and is responsible only to the country's top leader, Ayatollah Ali Khamenei.
While Iran has been involved in the wars surrounding Syria and neighboring Iraq, it has largely avoided the bloodshed of the region.
In 2009, more than 40 people were killed in a suicide attack in Sistan-Baluchestan province, including six Guards commanders. Jundallah, a pro-Sunni group still active in the Iranian border with Pakistan, took responsibility for the attack.
An attack on a military parade in Iran's southwest in September 2018 killed more than 20 people and wounded some 60.