Israel announced the launch of "precise strikes" on military targets in Iran on Saturday, in retaliation for attacks against it, as Iranian state media reported several explosions around the capital.

"In response to months of continuous attacks from the regime in Iran against the State of Israel - right now the Israel Defense Forces (Israeli military) is conducting precise strikes on military targets in Iran," the military said in a statement.

Israel had vowed, following Iran's October 1 missile attack, to hit back.

Hostilities between Iran and Israel soared since Israel launched it's offensive in Gaza last October, which has so far killed over 42,000 Palestinians.

Israel has since broadened the scope of its operations to Lebanon, vowing to secure its northern border after nearly a year of cross-border attacks by Lebanese group Hezbollah.

"Our defensive and offensive capabilities are fully mobilised," the Israeli military said in a statement.

Military spokesman Daniel Hagari in a separate statement called on the people to be "alert and vigilant".

Iranian state television said on Saturday "strong explosions" were heard around the capital, though it did not specify the cause of the blasts.

"Minutes ago, the sound of strong explosions were heard from around Tehran, the source of these sounds is not yet clear," a state TV presenter said.

Iranian media said no fire or explosions had been reported at a main oil refinery near Tehran.

The United States said strikes by its ally Israel on military targets in Iran are "an exercise of self-defence" following the attack earlier this month.

In a possible indication of the scope of Saturday's strike, Syrian state news agency SANA said Syrian air defences had intercepted what it described as "hostile targets" near the capital city, Damascus.

"Our anti-aircraft defence is confronting hostile targets in the skies around Damascus," SANA said on Telegram.

It also reported "sounds of explosions" in the vicinity of Damascus, though the origin of those blasts was unclear. (AFP)