Smoke in central Tehran
© ReutersSmoke is seen during a gunmen attack at the parliament's building in central Tehran, Iran, June 7, 2017
Iran's Revolutionary Guards have accused Saudi Arabia of masterminding the deadly attacks in Tehran on Wednesday, in which at least 12 people were killed. Earlier the terrorist group Islamic State claimed responsibility for the attacks.
"This terrorist attack happened only a week after the meeting between the U.S. president (Donald Trump) and the (Saudi) backward leaders who support terrorists. The fact that Islamic State has claimed responsibility proves that they were involved in the brutal attack,"
said the statement, as quoted by Reuters.

Earlier, Brigadier General Hossein Salami, IRGC deputy commander, pledged retaliation for the attack.
"Let there be no doubt that we will take revenge for today's attacks in Tehran, on terrorists, their affiliates and their supporters,"
he said, as cited by the news agency Mehr.

Meanwhile, Iranian President Hassan Rouhani said the attacks will make the country more united.
"Today's terrorist attacks in Tehran will make the Islamic Republic of Iran more determined in the fight against regional terrorism, extremism and violence,"
he said in a statement published by ISNA news agency.
"We will prove once again that we will crush the enemies' plots with more unity and more strength."
Twelve people were reported killed and 43 injured in gun and bomb attacks in the Iranian capital. The perpetrators targeted the Iranian parliament and Ayatollah Khomeini's shrine.

Both attacks were claimed by Islamic State (IS, formerly ISIS/ISIL), the jihadist organization based in Iraq and Syria. Iran supports both countries in their fight against IS.

IS also threatened Iran's majority Shiite population with more attacks, saying "the caliphate will not miss a chance to spill their blood" until Sharia law is implemented, Reuters reported.

The attacks in Tehran were the first that IS had claimed responsibility for in the Shiite Islamic republic.

The timing of the attacks, shortly after a presidential election in Iran, may indicate that the perpetrators want to cast doubt on the decision of the Iranian people to give President Hassan Rouhani a second term, Middle East expert Catherine Shakdam told RT.
"Iran has just conducted quite successfully its presidential election. Everything went according to plan, it was peaceful, it was progressive," she said.

"There is a clear desire to drive a narrative of fear and to make people have a sense of insecurity and doubt their officials and how they can protect their own borders.