Iranian Supreme Leader Ayatollah Ali Khamenei said on Friday the assassination of Quds Force chief Qassem Soleimani would double the motivation of the resistance against the United States and Israel, state television reported.

"All Enemies should know that the jihad of resistance will continue with a doubled motivation, and a definite victory awaits the fighters in the holy war," Khamenei said in a statement carried by TV, in which he called for three days of national mourning.

Iran often refers to regional countries and forces opposed to Israel and the United States as a "resistance" front.

"Soleimani's martyrdom will make Iran more decisive to resist America's expansionism and to defend our Islamic values. With no doubt, Iran and other freedom-seeking countries in the region will take his revenge," said Iranian President Hassan Rouhani in a statement, Iranian state television reported.

Iran will take crushing revenge for the assassination on Friday of Iranian Major-General Qassem Soleimani, the top commander of the elite Quds Force, Iranian Defence Minister Amir Hatami said, according to state news agency IRNA.

"A crushing revenge will be taken for Soleimani's unjust assassination ... We will take revenge from all those involved and responsible for his assassination," Hatami said.