Israel has carried out a strike inside Iran, a US official told CNN on Friday, in a move that threatens to further escalate conflict in the Middle East.

Iran’s air defense systems were activated in several locations after explosions were heard close to the airport and an army base in the province of Isfahan, state media reported early Friday morning.

Israel has not taken responsibility for the attack.

What Iranian reports say: Three blasts were heard near a military base where fighter jets are located in northwest Isfahan, Iran’s semi-official FARS news agency reported. Following the strike, Iranian media reported that all facilities around Isfahan are secure, including significant nuclear facilities in the area. Iran's National Cyberspace Center spokesman, Hossein Dalirian, said air defenses shot down three drones and "there are no reports of a missile attack for now."

What was the target? That remains unclear, but the US official told CNN the strike's target was not nuclear. According to FARS, a military radar was a possible target. Ghahjaworstan, where an explosion was heard, is located near Isfahan Airport and “the eighth hunting base of the Army Air Force,” FARS reported.

How did we get here? Tensions remain acute across the Middle East as Israel wages war in Gaza against Palestinian militant group Hamas, an Iranian ally. Meanwhile, a decades-long shadow conflict between Israel and Iran erupted into the open on the weekend when Iran launched an unprecedented attack on Israel that Tehran said was retaliation for a deadly suspected Israeli airstrike on Iran’s consulate in Syria.

What Israel says: The Israeli military said Friday they "don't have a comment at this time" when asked by CNN about reports of explosions in Iran. Israel's war cabinet has met periodically this week without announcing any definitive action following the Iranian strikes on Israel last weekend.

What the US says: Israel’s allies, including the United States, have called for restraint from Israel in a bid to prevent a regional war. The US "didn’t green light" an Israeli response, another senior US official told CNN. Prior to Friday's strike, the US expectation was that Israel would not target civilian or nuclear facilities, the second official said.

What happens next? That also remains unclear. Reports of the explosions came hours after Iran’s Foreign Minister Hossein Amir-Abdollahian told CNN that if Israel takes any further military action against Iran, its response would be “immediate and at a maximum level.” He added: “If the Israeli regime commits the grave error once again our response will be decisive, definitive and regretful for them.”

/CNN