The leader of Iran-backed militia Hizbollah in Lebanon has issued a call to "resistance fighters" around the world to punish those responsible for the killing of top Iranian commander Qassem Soleimani.

Hassan Nasrallah, in a speech delivered on Friday morning, said he would "continue on the path" of Soleimani, who headed the external operations Quds Force for the Revolutionary Guard Corp.

"Meting out the appropriate punishment to these criminal assassins... will be the responsibility and task of all resistance fighters worldwide," he said.

Soleimani, considered to be one of the most powerful and influential figures in the Islamic Republic, was killed alongside Abu Mahdi al-Muhandis, the deputy head of the Hashed al-Shaabi paramilitary force in Iraq, in a US air strike near Baghdad airport overnight.