A suicide bombing of a bus carrying Iranian Revolutionary Guard paramilitary elite troops killed at least 20 people and wounded 20 in the southeast, state media reported. According to reports, a Sunni extremist group operating across the border in Pakistan linked to al-Qaeda claimed the attack.
The bombing happened on the same day as a US-led conference in Warsaw was discussing what America calls the malignant influence of Iran throughout the Middle East. It also comes two days after the 40th anniversary of the 1979 Islamic Revolution and four decades of tense relations with the West.
Iranian Foreign Minister Mohammad Javad Zarif directly linked the meeting to the attack.
"Is not it a coincidence that Iran is affected by terror on the day the" Warsaw Circle "begins?" Zarif wrote on Twitter. "Especially when cohorts of the same terrorists cheer from the streets of Warsaw and support them with (Twitter) bots?"
The state news agency IRNA, citing an "informed source", reported on the attack on the Guards in the Iranian province of Sistan and Balochistan.
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 Guard is an important economic and military power in Iran and is responsible only to the country's top leader, Ayatollah Ali Khamenei. Later, a statement was issued stating that a vehicle loaded with explosives was aimed at a bus carrying border guards attached to its troops.
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 by Sunni extremists in Sistan and Baluchistan province, including six Guards commanders. Jundallah, a Sunni extremist group still active in the Iranian border with Pakistan, took responsibility for the attack.
Recently, another Sunni-extremist group, Jaish al-Adl, has linked Al Qaeda and abducted eleven Iranian border guards in October. Five were later returned to Iran and six remained firm.
Both official and semi-official Iranian media on Wednesday accused the bombing of Jaish al-Adl, the "Army of Justice," saying the group had claimed the attack.
Founded in 2012, this group attracted some Jundallah militants, experts say. Iran has long suspected Saudi Arabia of supporting the fighters, which Riyadh denies. It is also unclear how the militants have been able to operate free of Pakistan for years.
A June 7, 2017 coordinated attack by the group of Islamic states on the parliament and shrine of Ayatollah Ruhollah Khomeini, the leader of the Islamic Revolution in Iran, has killed at least 18 people and injured more than 50.
And last September militant soldiers disguised as soldiers opened fire on a military parade in the oil-rich southwestern city of Ahvaz in Iran. Twenty-four people were killed and over 60 wounded.
Arab separatists in the region took responsibility, as did the Islamic State group.
The attacks come when Iranian officials said they blamed Saudi Arabia and the United States for causing dissent in the country. President Donald Trump, who pledged to break off Tehran's nuclear deal with the world powers, withdrew the US from the agreement last May. Since then, the United Nations has claimed that Iran has been able to maintain its side of the agreement, although Iranian officials are increasingly threatened with renewed enrichment.
The new tensions continued to challenge Iran's already weakened economy. There were also sporadic protests in the country, incidents that were greeted by Trump in the midst of Washington's maximalist approach to Tehran.
Khamenei, who had previously approved the deployment of President Hassan Rouhani in the wake of the nuclear negotiations in the West, rejected any future dealings with the US.
"In the United States, solving problems is inconceivable, and negotiating with them will only cause material and mental harm," Khamenei said in a statement.
The Warsaw Summit, which began on Wednesday, was originally focused on Iran. However, the US later managed to further expand the Middle East to increase participation.
Zarif predicted that the Warsaw Summit would not be productive for the US.
"I think it's dead on arrival or dead before arrival," he said at a press conference before the bombing.