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.

When asked by a reporter during a press briefing whether Iran would consider enriching uranium to weapons-grade 90% purity, the foreign ministry spokesman gave a vague response.

“The level, amount and quality of enrichment are in line with the needs of Iran’s peaceful nuclear program,” Saeed Khatibzadeh said. “All these measures have been taken with the knowledge of the International Atomic Energy Agency and will continue to be so in the future.”

His comment came after Iran’s hard-line Kayhan newspaper published an editorial arguing that Iran should enrich uranium up to 90% purity and become a “world nuclear power” if negotiations in Vienna fail to grant the country sanctions relief.

Since former President Donald Trump pulled America out of the nuclear deal and reimposed crushing sanctions, Tehran has started enriching uranium up to 60% purity — a short technical step from the 90% needed to make an atomic bomb.

Iran insists that its nuclear program is peaceful. But the country’s steps away from its obligations under the 2015 accord have alarmed its archenemy Israel and other world powers. Israel has repeatedly threatened unilateral action against Iran’s nuclear program.

On Monday, 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.

(AP)