Iran said on Monday that sounds heard near its Bushehr nuclear power plant were related to an air defence drill, Iranian state media reported, while warning that Tehran would give a "crushing response" to any Israeli attack.
"This air defence exercise took place at 5 a.m. (0130 GMT) with full preparation and coordination with the armed forces," Bushehr's deputy governor Mohammadtaqi Irani told Iranian state media.
Some media outlets reported earlier that anti-aircraft fire had been heard in the area.
Earlier this month, Iranian authorities said air defences had fired a missile as part of a military drill after state media reported a large explosion above the central town of Natanz, which houses Iran's main nuclear facility.
Iran has accused Israel of several attacks on facilities linked to its nuclear program, including the one in April at the Natanz site, and of killing its nuclear scientists, over the past years. Israel has neither denied nor confirmed the allegations.
Opposing efforts by world powers to revive Iran's 2015 nuclear, Israel has long threatened military action against its arch enemy, Iran, if diplomacy fails to prevent it from acquiring a nuclear bomb. The Islamic Republic says its nuclear ambitions are peaceful.
Israel is widely believed to have the Middle East's only nuclear arsenal.
Iran has warned of a "crushing" response to any Israeli move against it.
"If Israel carries out attacks against Iran, our armed forces will immediately attack all centres, bases, routes, and spaces used to carry out the aggression," said Gholamali Rashid, a senior commander of Iran's Revolutionary Guards.
"Any threat to Iran's nuclear sites and military bases by the Zionist regime (Israel) is not possible without the green light of America."
Indirect talks between Iran and the United States to reinstate the nuclear pact have made little discernible progress since they resumed last month for the first time since Iran's hardline president, Ebrahim Raisi, was elected in June.
The talks are expected to resume this year, while some officials have mentioned 27 December as a tentative date.
"In the coming days, the coordinator of nuclear talks (the European Union's Enrique Mora) will announce the exact date," Iranian Foreign Ministry spokesman told a news conference.
The 2015 deal lifted sanctions against Tehran in return for tough restrictions on Iran's nuclear activities aimed at extending the time Tehran would need to obtain enough fissile material for a nuclear bomb if it chose to - so-called breakout time - to at least a year from roughly two to three months.
In response to Trump's "maximum pressure" policy, Iran in 2019 started gradually breaching the deal's nuclear restrictions and pressing ahead further with its atomic activities. Tehran says its nuclear steps are reversible if all sanctions are lifted in a verifiable process.