"Meting out the appropriate punishment to these criminal assassins... will be the responsibility and task of all resistance fighters worldwide," Hassan Nasrallah said in a statement.

"We who stayed by his side will follow in his footsteps and strive day and night to accomplish his goals," the leader of powerful Shiite militant group said.

"We will carry a flag on all battlefields and all fronts and we will step up the victories of the axis of resistance with the blessing of his pure blood," Nasrallah said.

The "axis of resistance" is a term that refers to an alliance formed by Iran, Syria and Hezbollah to fight against Israel and the Western military presence in the region.

The heavily armed Hezbollah group controls whole neighbourhoods in Beirut and most of the south of Lebanon, including the area bordering Israel.

It also has fighters deployed in Syria and Iraq who were operating under Soleimani's command.