TEHRAN, Iran - A deadly suicide bombing has claimed the lives of at least 27 members of Iran's elite Revolutionary Guards.
Another thirteen guards were injured in the explosion, many of them seriously.
The attack took place on Wednesday in southeastern Iran, in the largely populated Sistan and Baluchistan province.
The Islamic Revolutionary Guard Corps said in a statement, a bomb-laden vehicle targeted a bus carrying around 40 of its personnel.
The Sunni group Jaish al-Adl ("Army of Justice") has claimed responsibility for the attack.
"Is it no coincidence that Iran is hit by terror on the very day that #WarsawCircus begins?" Iran's Foreign Minister Javad Zarif tweeted late Wednesday.
"Especially when cohorts of same terrorists cheer it from Warsaw streets & support it with Twitter bots? US seems to always make the same wrong choices, but expect different results," Zarif's post said.
A number of Arab countries have joined Israel and other Western states in Warsaw for a two-day conference organised by the U.S. to discuss security and peace in the Middle East. The meeting has been termed a 'Ministerial to Promote a Future of Peace and Security in the Middle East.'
Palestinian factions meeting in Moscow earlier criticised the meeting.
Israeli Prime Minister Benjamin Netanyahu, who is in Warsaw for the meeting, meantime has come under attack for a tweet he posted, which he has since deleted and replaced.
The original tweet said: "What is important about this meeting, and it is not in secret, because there are many of those - is that this is an open meeting with representatives of leading Arab countries that are sitting down together with Israel in order to advance the common interest of war with Iran."
After coming under fire, the Israeli prime minister hastily deleted the post and put up another, replacing the words 'war with Iran' with 'combating Iran.'