Iran has yet to decide whether to join a sixth round of nuclear talks with the United States on Sunday, state media reported, as Israel and Iran traded fire for a second day.

Israel targeted Iran's air defenses and missile launchers on Saturday as it pressed its bid to dismantle its arch-foe's military capabilities, after a night of mutual attacks.

Israel's massive strikes on Iran, which it calls an existential threat, have hit nuclear and military facilities, killed top commanders and dozens of civilians, and sought to destroy the country's defense capabilities.

Iranian state media said the country's forces downed two Israeli fighter jets on Friday, during a massive Israeli air raid.

"At least two Israeli fighter jets were shot down in Iranian skies," the official IRNA news agency reported, without elaborating.

An Israeli military official said Iran launched on Friday dozens of ballistic missiles at Israel, as sirens sounded and AFP journalists reported loud blasts heard in Jerusalem and Tel Aviv.

"A short while ago, the IDF identified missiles launched from Iran toward the territory of the State of Israel," it said in a statement, adding the public should enter protected shelters "and remain there until further notice".

Russian President Vladimir Putin condemned Israel's wave of strikes launched at Iran, the Kremlin said on Friday, as he held separate phone calls with Israeli Prime Minister Benjamin Netanyahu and Iranian President Masoud Pezeshkian.

"Vladimir Putin stressed that Russia condemns Israel's actions, which violate the UN Charter and international law," the Kremlin said in a statement, adding that Putin told Netanyahu of his "readiness to provide mediation" to prevent further escalation.

France could help defend Israel against an attack from Iran "if in a position to do so", French President Emmanuel Macron said on Friday.

"If Israel were to be attacked in retaliation by Iran, France, if in a position to do so, would take part in protection and defense operations," he said during a press conference.

Iranian air defenses intercepted "projectiles" over the capital Tehran on Friday, state media said, as Israel vowed to keep up pressure after a wave of strikes on military and nuclear sites.

"Enemy projectiles were intercepted by the Tehran air defense," state news agency IRNA said, with another agency, ISNA, reporting that "the air defense systems of Tehran successfully shot down targets".

Several explosions were heard in Tehran and surrounding areas Friday evening, Iranian state media reported, more than 12 hours after a massive wave of Israeli attacks on the country.

"There were reports of explosions heard in the west of Tehran province," in the cities of Shahriar and Malard and around the neighborhood of Chitgar in Tehran city, state news agency IRNA reported, while Mehr agency reported a blast in Pakdasht southeast of the capital.

Israel's military said on Friday it had begun deploying reservists "to all combat arenas throughout the country" after launching a wave of strikes on military and nuclear sites in Iran.

The military said in a statement that it "began to deploy reservists from different units to all combat arenas throughout the country", calling it part of "preparations for defense and offence across all arenas".

World leaders urged restraint on Friday after Israel pounded Iran, striking 100 targets including nuclear and military sites, and killing senior figures.

Here is a roundup of key reactions: