Israel hit back at Iran early on Saturday, saying its military was conducting strikes against military targets, as Iranian media reported multiple explosions.

The Middle East has been on edge in anticipation of Israeli retaliation for a ballistic-missile barrage carried out by Iran on Oct. 1, in which around 200 ballistic missiles were fired at Israel, Iran's second direct attack on Israel in six months.

Those strikes came after Israel killed the top leadership of Iranian ally Hezbollah in Lebanon. Hezbollah militants joined the fight against Israel in support of Hamas, the Palestinian militant group based in Gaza, also aligned with Iran, that attacked Israel on Oct. 7, 2023.

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

Israel has the right and duty to respond to attacks from Tehran and its proxies, which have included missile strikes launched from Iranian soil, the military said.

"Our defensive and offensive capabilities are fully mobilized," it added.

The scope of the attack was not immediately clear, but an Israeli public broadcaster said dozens of fighter jets were striking military targets.

Targets did not include energy infrastructure or nuclear facilities, NBC News and ABC News reported, citing an Israeli official. U.S. President Joe Biden had warned that Washington, Israel's main backer and supplier of arms, would not support a strike on Tehran's nuclear sites and has said Israel should consider alternatives to attacking Iran's oil fields.

The semi-official Iranian Fars news agency said several military bases in the west and southwest of Tehran had been targeted by Israel.

Iran's state TV said several strong explosions were heard around the capital Tehran. Semi-official Iranian media said explosions were also heard in the nearby city of Karaj.

State TV cited unnamed Iranian intelligence officials as saying that the origin of the explosions "could be from the activation of Iran's air defense system."

Iranian authorities have repeatedly warned Israel against launching an attack, saying any strike on Iran would be met with a stronger retaliation.

Prime Minister Benjamin Netanyahu and Defense Minister Yoav Gallant were at the military headquarters in Tel Aviv, Netanyahu's office said.

The United States was notified by Israel ahead of its strikes on targets in Iran but was not involved in the operation, a U.S. official told Reuters.

"We understand that Israel is conducting targeted strikes against military targets in Iran as an exercise of self-defense and in response to Iran's ballistic missile attack against Israel on October 1st," said White House National Security Council spokesperson Sean Savett.

Fears that Iran and the U.S. would be drawn into a regional war have risen with Israel's intensifying assault on Hezbollah since last month, including airstrikes on Beirut and a ground operation, as well as its year-old conflict in the Gaza Strip.

U.S. Secretary of State Antony Blinken said on Wednesday that Israel's retaliation should not lead to greater escalation.

Syrian state TV said explosions were also heard in the Damascus countryside and central region.

Israel's defense minister said this week that enemies would "pay a heavy price" for trying to harm Israel.