Iranian President Hassan Rouhani blamed the United States and its regional allies, namely Israel, on Thursday for a suicide bombing in southeastern Iran that killed at least 27 members of the country's elite Revolutionary Guards, Iranian state TV reported.
The force said on Wednesday a suicide bomber driving a vehicle laden with explosives had attacked a bus transporting members of the Guards in the province of Sistan-Baluchestan.
A militant Sunni Muslim group, Jaish al Adl (Army of Justice), which says it seeks greater rights and better living conditions for the ethnic minority Baluchis, has claimed responsibility for the attack, Iranian media have reported.
"The crime will remain as a 'dirty stain' in the black record of the main supporters of terrorism in the White House, Tel Aviv and their regional agents," Rouhani said.
Apart from Israel, Rouhani did not name the regional states he believed were to blame. Mainly Shiite Muslim Iran does not recognize Israel, which is a key U.S. ally in the region and sees Tehran as posing an existential threat to its existence.
The heavy losses among Iran's premier military force prompted a senior Revolutionary Guards commander to issue a warning to the country's foes.
"Our response in defense of the Islamic Revolution will not be limited to our borders," Ali Fadavi was quoted as saying by Fars.
"The enemies will receive a very firm response from the Revolutionary Guards like before." He did not specify which enemies or what actions Tehran would take.
In the past, Iran has accused its regional rival, Sunni Arab Saudi Arabia, of supporting Sunni separatist groups who have attacked its security forces. Riyadh has denied the charges.
Iran's Shiite Muslim authorities say militant groups operate from safe havens in Pakistan and have repeatedly called on the neighboring country to crack down on them.
While Sunni terrorist groups are not regarded as a major threat, the attack dealt a fresh blow to Iran's security establishment, which has often said it can repel any threat no matter how big, even from the United States and its ally Israel.
The assault in impoverished Sistan-Baluchistan province illustrated that Iran's elite force, which answers directly to Supreme Leader Ayatollah Ali Khamenei, can be vulnerable to guerrilla-style operations.
The Guards' estimated 125,000-strong military, with army, navy and air units, has acted as the sword and shield of Shiite clerical rule in Iran since its 1979 Islamic Revolution.
The force also operates outside of Iran's borders in countries such as Iraq and Syria where it works with proxies to promote Tehran's interest. It runs a business empire in Iran worth billions of dollars.
"The self-sacrificing military and intelligence children of the people of Iran will take revenge for the blood of the martyrs of this incident," Fars quoted Foreign ministry spokesman Bahram Qassemi as saying.
Iranian Foreign Minister Mohammad Javad Zarif appeared to blame the United States for the attack, citing a U.S.-sponsored conference in Warsaw aimed at rallying support to further isolate Iran.
On Twitter he asked: "Is it no coincidence that Iran is hit by terror on the very day that #WarsawCircus begins?"
