Israel launched airstrikes early Monday targeting central and western Iran in response to missile fire.
Iranian state television reported the sound of explosions being heard in Isfahan, Tabriz and Tehran, without immediately elaborating.
The attacks further strain efforts to reach a permanent ceasefire in the war between Iran and the United States.
Earlier, Iran launched missiles at Israel in the first such bombardment since a fragile ceasefire took effect in early April.
The exchange raised the possibility of a return to heavy fighting and complicating mediation efforts to end the war.
