Iran's advanced S-300 air defence system, delivered by Russia following a July 2015 nuclear deal after years of delay, is now operational, state television reported on Saturday.
Iran had been trying to acquire the system for years to ward off repeated threats by Israel to bomb its nuclear facilities, but Russia had held off delivery in line with UN sanctions imposed over the nuclear programme.
"The S-300 air defence system has been tested... in the presence of government and military officials," the television said.
It said that the test at a desert base had seen several targets, including a ballistic missile and a drone, intercepted.
"The S-300 is a system that is deadly for our enemies and which makes our skies more secure," he said.
Iran's activation of the defence system comes amid mounting tensions with the new US administration of President Donald Trump, who imposed sanctions after Iran tested a medium-range ballistic missile in January.
The deal to buy the S-300 system was originally signed in 2007 but Russia suspended it in 2010 citing a UN ban on arms sales to Iran.
It was revived after the nuclear deal between Iran and major powers went into effect in January last year.
In August, state television aired footage of the system being installed around the Fordo nuclear site in a mountain near Qom, south of the capital.