Iran accused Israel, backed by the US, of attacking residential areas in a series of airstrikes in the early morning of June 13, killing many people.
Tehran has said it has put its military in a 100% readiness state and has said it will respond to Israel with a "thunderstorm".
On the morning of June 13, Major General Abolfazl Shekarchi, a spokesman for the Iranian Armed Forces, said: The enemy of Israel launched an attack with the support of the US and targeting residential areas. They will pay a heavy price.
He said Iran had put its entire army 100% combat ready, asserting that "the enemy will soon receive a strong attack".
The first explosions were recorded at around 3am on June 13 local time in the capital Tehran, then spread to many other provinces and cities such as Khorramabad, Khondab and Natanz.
On social media, a series of videos have been circulating showing residential areas heavily destroyed - a clear sign of an attack that did not discriminate on targets.
The Israeli government confirmed it was behind the attack, saying it targeted locations related to Iran's nuclear and missile programs. However, Tehran strongly opposed the attack, saying that the target of the attack was mainly residential areas and civilian facilities.
According to Iranian state media, several senior commanders of the Islamic Revolutionary Guard Corps (IRGC), including General Hossein Salami - Commander of the IRGC - and leading nuclear scientists, were also among those killed in large-scale airstrikes.
Brett McGurk, a former Middle East coordinator of the White House under President Joe Biden, said Iran is fully capable of launching a large-scale response.
He said Iran fired more than 200 ballistic missiles at Israel in the attack on October 1, 2024. Although largely intercepted, Iran's ability to launch a series of warships is "very formidable".
If well prepared, Iran could launch a series of 30 missiles a few minutes apart, and it would take only about 13 minutes to reach Israel, according to McGurk. The problem is whether they have enough organization to do it in the context of military leadership casualties, he added.
With Israel confirming that it was behind the series of attacks and Iran declaring a counterattack, regional tensions are escalating to an unprecedented level. Many experts worry that a direct military confrontation between the two countries - with the involvement of the US behind or behind - could turn the entire Middle East into a hot battlefield.
