Iran vowed quick revenge after ISIS suicide bombers and gunmen stormed parliament and the mausoleum of the country’s revered spiritual leader Ayatollah Ruhollah Khomeini, killing 13 people and injuring 41.

That revenge is likely to be swift and brutal based on the response to past terror attacks in the country, and won’t be tempered by the fact that all five attackers were killed by security forces. And it might not even be entirely aimed at preventing future terrorist attacks.

Iran’s Powerful Revolutionary Guard stopped short of directly blaming Saudi involvement but called it “meaningful” that the attacks took place a week after President Donald Trump traveled to Riyadh. The Guard statement said that Saudi Arabia “constantly supports takfiri terrorists” and the Islamic State’s claim of responsibility for the Tehran attacks “reveals [Saudi Arabia’s] hand in this barbaric action.”

IRAN ATTACK: ISIS CLAIMS RESPONSIBILITY FIR PAIR OF ASSAULTS IN TEHRAN

Iran is not limiting its focus to external threats. Iranian human rights campaigners say hardline politicians and news outlets close to the Islamic Revolutionary Guard Corps (IRGC) have already begun placing blame for the Tehran attacks on reformist and centrist officials who have been critical of Iran’s security forces.

And they fear that the attack will be used as an excuse to further muzzle speech.

“These terrible events should not undermine the mandate to improve civil and political rights that the Iranian people handed President Hassan Rouhani in the recent election,” said Hadi Ghaemi, executive director of the Center for Human Rights in Iran (CHRI). “Despite the threat Iran is facing, the Iranian authorities should not use the attacks as an excuse to further crackdown on civil society.”

While it was the first attack the Islamic State carried out in Tehran, it’s not the first time Iran has criticized the Saudis for terror attacks by other groups. Predominantly Shiite Iran has been dealing with a Sunni resistance movement in the Baluchestan and Sistan provinces along the border shared with Pakistan and Afghanistan. The area has been a warzone for years, with thousands of Iranian troops killed in clashes with Sunni terrorists as well as smugglers transporting heroin through Iran and Turkey to Europe.

For example, a few years ago Iran executed 16 “Sunni insurgents” after 14 Iranian border guards were killed in a clash. It’s unclear whether the Sunnis were rounded up or already in custody, but reports said “they were not believed to be connected to the border attack.”

More recently, Iran executed 10 Sunni prisoners – it calls them “Takfiri-Salafist” – held on terror charges despite claims they were innocent. The Norway-based group Iran Human Rights claimed their confessions were forced.

“Many if not all of these prisoners were subjected to unfair trials and sentenced to death based on confessions extracted under torture,” IHR’s spokesman, Mahmood Amiry-Moghaddam, told the Guardian newspaper last year.

Iranian human rights campaigners are worried the ISIS attack is going to lead to yet another crackdown.

“Whenever the Iranian state has perceived external threats,” the CHRI said in a statement to Fox News, “the intelligence establishment has seized the opportunity to further infringe upon the civil rights of the Iranian people.”