Iran has accused its regional rival Saudi Arabia of plotting the twin attacks on its parliament and a shrine in Tehran. Iran's Revolutionary Guard Corps (IRGC) has vowed that the suicide bombing and gun attack would get a stinging response.

The coordinated attacks, led by four unidentified men, targeted two main buildings in the Iranian capital and claimed 13 lives on Wednesday (7 June). The Isis has claimed responsibility for the incident.

"The fact that Islamic State has claimed responsibility proves that they were involved in the brutal attack," the elite Iranian force said in a statement referring to the Saudi kingdom.

"The public opinion in the world, specially the Iranian nation sees this terrorist action that happened a week after the joint meeting of the US president with the heads of one of the reactionary regional states that has constantly been supporting Takfiri terrorists as to be very meaningful, and believes that Isis' acknowledging the responsibility indicates their complicity in this wild move," the IRGC said.

Iran – a theocratic nation following the Shia school of Islam and a regional heavyweight – has a fractious relationship with the ultra-conservative Sunni-majority Saudi Arabia. Their relations are strained over a series of religio-political issues such as the way Islam is interpreted, the Islamic world's leadership and oil exports.

"The IRGC has proved that it would not leave unanswered the shedding of innocent blood and it ensures the Iranian nation that it will not hesitate even for a moment to protect the country's national security and the lives of the dear people, as it killed all these terrorists with the help of the Law Enforcement Force today," the Iranian forces added.

Riyadh has rejected Iran's allegations and called them baseless. Saudi Arabia's Foreign Minister Abel al-Jubeir said there is no evidence to show that Saudi citizens are involved in the attack.

Iran parliament attack
Members of Iranian forces take cover during an attack on the Iranian parliament in central Tehran, IranReuters