Iran will give a “calculated and decisive” response to the killing of its top nuclear scientist, said a top adviser to Iran’s supreme leader, while a hardline newspaper suggested Tehran’s revenge should include striking the Israeli city of Haifa.

“Undoubtedly, Iran will give a calculated and decisive answer to the criminals who took Martyr Mohsen Fakhrizadeh from the Iranian nation,” Kamal Kharrazi, who is also head of Iran’s Strategic Council on Foreign Relations, said in a statement.

Fakhrizadeh, long suspected by Western and Israeli government of masterminding a secret nuclear weapons programme, was ambushed on a highway near Tehran on Friday and gunned down in his car.

Iran’s clerical and military rulers have blamed the Islamic Republic’s longtime enemy, Israel, for the killing. Iran has in the past accused Israel of killing several Iranian nuclear scientists since 2010.

Prime Minister Benjamin Netanyahu’s office has declined to comment on the killing. An Israeli cabinet minister, Tzachi Hanegbi, said on Saturday he did not know who carried it out.

Iranian hardline media called on Sunday for tough revenge.

The hardline Kayhan daily, whose editor-in-chief is appointed by Supreme Leader Ayatollah Ali Khamenei, called for an attack on the Israeli port city of Haifa, if an Israeli role in Fakhrizadeh’s killing is proven.

“The attack should be carried out in such a way that in addition to destroying the facilities, it should also cause heavy human casualties,” wrote Saadollah Zarei in an opinion piece.

However, Iran’s rulers are aware of daunting military and political difficulties of attacking Israel. Such an attack would also complicate any effort by United States President-elect Joe Biden to revive detente with Tehran after he takes office on January 20.

Tensions have been high between Tehran and Washington since 2018, when President Donald Trump exited Iran’s 2015 nuclear deal with six major powers and reimposed sanctions that have hit Iran’s economy hard. In retaliation, Tehran has gradually breached the deal’s curbs on its nuclear programme.

Biden has said he will return the US to the deal if Iran resumes compliance. Iran has always denied pursuing nuclear weapons.