TEHRAN, Iran (AP) — Iran's paramilitary Revolutionary Guard staged a major military exercise across the country's south on Monday amid heightened tensions over Tehran's nuclear program, state TV reported.

The Guard’s aerospace division, ground troops and naval forces joined in the five-day drill, the report said, with maritime forces set to maneuver in the strategic Strait of Hormuz, the narrow gateway for 20% of the world's traded oil.

The exercise comes days after talks to revive Tehran's tattered nuclear deal with world powers broke up in Vienna. Iran has accelerated its nuclear advances as negotiations to return to the accord struggle to make headway, alarming Israel and other regional rivals. Israel has repeatedly threatened unilateral action against Iran's nuclear program.

Gen. Gholamali Rashid, a top Guard commander, vowed a harsh response to any Israeli military action against Iran.

Iranian forces will launch “a crushing attack on all bases, centers, paths and space used to carry out the aggression without delay,” the semi-official Mehr news agency quoted him as saying.

“Any threat to Iran’s nuclear and military bases by the Zionist regime is not possible without the green light support of the United States," he said.

Earlier on Monday, residents in Bushehr, some 700 kilometers (440 miles) south of Iran’s capital, Tehran, reported seeing a light in the sky and hearing a loud explosion near the Bushehr nuclear power plant.

It was the second time this month that sudden anti-aircraft firing erupted the middle of the night near an Iranian nuclear facility, which Iranian forces hours later described as drill for its surface-to-air missile defense system.