Two explosions were heard early Friday off the coast of Sirik County in southern Iran's Hormozgan province, the country's state-run IRIB news agency reported.
It said the explosions were from the sea and related to the Strait of Hormuz.
There have been no projectile hits or clashes in Sirik so far, it said.
Two blasts were also heard in the port city of Bandar Abbas in Hormozgan, it added.
Meanwhile, Iran's semi-official Tasnim news agency reported that the explosions around Sirik may relate to Iranian armed forces' response to "a violation during passage through the Strait of Hormuz".
Iran's main military command, Khatam al-Anbiya Central Headquarters, announced early Thursday that the Strait of Hormuz has been closed to all vessels, including oil tankers and commercial ships, due to security threats in the waterway.
In a statement carried by Iranian media, the headquarters cited ongoing U.S. "malicious acts" and attacks earlier in the day on areas in Iran's southern Hormozgan province, warning that any vessel attempting to transit the strait will be targeted.
However, U.S. Central Command denied the strait was closed, saying Wednesday that commercial vessels continue to transit the Strait of Hormuz.
In a statement, Iran's Islamic Revolution Guard Corps (IRGC) Navy reminded all ships to remain at anchor, not to be misled by the U.S. military into passing through the strait without authorization.
Blasts heard near south Iran's Sirik, Bandar Abbas: media
U.S. stocks closed higher on Thursday after U.S. President Donald Trump announced he had called off planned strikes on Iran scheduled for the evening.
The Dow Jones Industrial Average rose 929.97 points, or 1.86 percent, to 50,848.75. The S&P 500 added 127.31 points, or 1.75 percent, to 7,394.30. The Nasdaq Composite Index increased by 640.158 points, or 2.54 percent, to 25,809.66.
Eight of the 11 primary S&P 500 sectors ended in the green, with materials and industrials leading the gainers by rising 3.26 percent and 3.25 percent, respectively. Energy and consumer staples led the laggards by decreasing 2.06 percent and 0.47 percent, respectively.
Oil prices dropped after Trump wrote on Truth Social that he had "cancelled the scheduled strikes and bombings against Iran this evening."
The West Texas Intermediate for July delivery lost 2.32 U.S. dollars, or 2.58 percent, to settle at 87.71 dollars a barrel on the New York Mercantile Exchange. Brent crude for August delivery decreased by 2.72 dollars, or 2.92 percent, to settle at 90.38 dollars a barrel on the London ICE Futures Exchange.
Chipmakers led the advance, with notable gains in Micron Technology, Advanced Micro Devices, and Intel, which helped offset earlier pressure on the technology sector.
On the economic front, wholesale inflation for May came in higher than expected, the U.S. Bureau of Labor Statistics reported. The producer price index for final demand rose 1.1 percent from the previous month and 6.5 percent from a year earlier.
In corporate news, Oracle dropped 8.53 percent despite reporting quarterly earnings that beat analyst expectations, as investors reacted to disappointing cloud revenue growth and the company's plans for an equity and debt offering.
The market's primary focus this week remains Friday's highly anticipated public debut of Elon Musk's SpaceX, which is expected to be the largest initial public offering in history.
U.S. stocks rebound after Trump calls off strikes on Iran
