Iran's President Masoud Pezeshkian said on Sunday that Israel made a "great mistake" in assassinating Ismail Haniyeh, the head of the Hamas political bureau, in Tehran, and that it will "not go unanswered."
He made these remarks in a meeting with Jordanian Foreign Minister Ayman Safadi in Tehran, who delivered a message from King Abdullah II to the new Iranian president.
The Jordanian top diplomat arrived in the Iranian capital on Sunday to hold talks with Iranian leaders amid heightened regional tensions following Haniyeh's assassination.
It was the first official visit to Iran by a Jordanian foreign minister since 2015.
Pezeshkian said Iran expects all Islamic countries to "strongly condemn such crimes," vowing that Haniyeh's assassination will not remain unanswered.
The newly-elected Iranian president added that the cornerstone of his government's foreign policy is to "expand and strengthen peace, tranquility, and stability in the region and around the world."
He emphasized the need for unity among Islamic countries to stop the "aggression and crimes" of Israel against Palestinians in the besieged Gaza Strip.
Earlier, Safadi held wide-ranging talks with Iran's interim Foreign Minister Ali Bagheri Kani at the Foreign Ministry.
Bagheri Kani said Haniyeh's assassination was "against all international, legal, and customary norms" and violated "regional and international security and stability, as well as the territorial integrity and national sovereignty of the Islamic Republic, making a decisive response to this crime more essential than ever," according to a statement from the Foreign Ministry.
He condemned the stance of Western countries, led by the US and some European states, for "backing the crimes of the Zionist regime and preventing the issuance of even a single statement in the UN Security Council condemning the recent terrorist crime of this regime."
The interim top diplomat emphasized that Israel must "receive a strong and decisive response to understand that security barbarism has heavy costs."
In his post-meeting remarks, Safadi said he informed his Iranian counterpart that he was not carrying any message from Israel or any other country to Iran, or vice versa.
He said his trip to Tehran was undertaken with the clear goal of "resolving disputes between the two countries in a manner that ensures our mutual interests."
Safadi stressed that the first step to prevent the escalation of regional tensions is to stop Israeli attacks on the Gaza Strip.
In a statement issued earlier in the day, Jordan's Foreign Ministry confirmed his visit to Tehran to deliver a message from King Abdullah II to Iran's newly elected president.
The visit came amid hectic regional diplomatic efforts to de-escalate the situation following the assassination of Hamas' political bureau leader.
Haniyeh, who was in the Iranian capital to attend the swearing-in ceremony of Pezeshkian, was killed in an attack that targeted his residence in a high-security zone of north Tehran early on Wednesday.
The Islamic Revolutionary Guard Corps (IRGC) in a statement on Saturday said the attack was "planned and executed" by Israel with US support, using a "short-range projectile" fired from outside the residence.
The IRGC has warned that Israel will receive a "severe punishment in due time and place." Israel has neither confirmed nor denied its role in the attack, while the US has said it was unaware of it and was not involved.
Calling for de-escalation of tensions, many foreign officials have spoken to Bagheri Kani since Wednesday, including Safadi, who has spoken to him twice in the past 48 hours.
On Saturday, Bagheri Kani said in a post on X that he had conversations with top diplomats of Jordan and Egypt and that the situation in West Asia was "sensitive" due to Israel's "continuation of crimes and dangerous adventures."
"Iran's determination to hold the regime accountable is serious," he wrote, pointing to military retaliation, which looks imminent.