Iran's President Ebrahim Raisi on Friday hailed Tehran's unprecedented retaliatory attack on Israel almost a week ago but did not mention explosions heard in his country's central region.

World leaders called for de-escalation after United States media quoted officials saying Israel had carried out retaliatory strikes on Iran, after the Islamic republic's missile and drone attack against Israel.

That operation "showed our authority, our people's will of steel and our unity," Raisi told hundreds of people in Semnan province, east of Tehran.

In the speech, he did not refer to the blasts, and there has been no official reaction either from Iranian or Israeli officials.

The blasts resounded early Friday in the central province of Isfahan, state media said.

Iran's space agency spokesman Hossein Dalirian, referring to a type of drone, said there was "a failed and humiliating attempt to fly quad-copters, which were shot down."

In a post on X, formerly Twitter, he denied Iran had been attacked from abroad.

"There have been no air attacks from outside the borders against Isfahan or other parts of the country so far," he said.

Iran's army commander-in-chief Abdolrahim Mousavi attributed Friday's explosions to "the firing of anti-aircraft defence systems on a suspicious object."

He said there was "no damage" and that investigations were underway to assess the scale of the incident, according to Tasnim news agency.

Overnight last Saturday-Sunday Iran carried out its first-ever attack directly targeting Israel.

The attack was in response to an April 1 air strike that levelled Tehran's consular annex in Damascus and killed seven Revolutionary Guards members, including two generals.

rkh/mz/it