Online retailer Digikala - Iran's equivalent of Amazon - said it sold 75,000 masks within a 36-hour period
Iran on Saturday reported one more death among 10 new cases of coronavirus, bringing the total number of deaths in the Islamic republic to five - the highest of any country outside the Far East.
Since it emerged in December, the virus has killed 2,345 people in China, the epicentre of the epidemic, and 16 elsewhere in the world.
The COVID-19 outbreak in Iran first surfaced on Wednesday, when authorities said it claimed the lives of two elderly people in Qom, a Shiite holy city south of the capital.
They were the first confirmed deaths from the disease in the Middle East.
"We have 10 new confirmed cases of COVID-19," Iran's health ministry spokesman Kianoush Jahanpour told state television on Saturday.
"One of the new cases has unfortunately passed away," he added, noting that eight of them had been hospitalised in Qom and two in Tehran, without specifying where the death occurred.
The latest cases take to 28 the total number of confirmed coronavirus infections in Iran.
The outbreak emerged in the lead-up to a parliamentary election on Friday.
State media said the disease had failed to dampen "the revolutionary zeal of Qom's people" to turn out to vote.
Iranians have been snapping up surgical face masks in a bid to avoid catching the virus.
Online retailer Digikala - Iran's equivalent of Amazon - said on Friday that it had sold 75,000 masks within a 36-hour period.
It said it was not claiming a commission on its mask sales, amid concerns that demand was causing prices to skyrocket on the black market.
"Besides the high demand, we stand against the unusual price increase," Digikala tweeted.
"We stand alongside our dear suppliers and by providing fresh supplies, we hope we can meet a part of the country's demand."
The health ministry said tests had been carried out on 785 suspected coronavirus cases since the outbreak began.
"Most of the cases are either Qom residents or have a history of coming and going from Qom to other cities," its spokesman said.
Iran has yet to confirm the origin of the outbreak, but one official speculated that it was brought in by Chinese workers.
"The coronavirus epidemic has started in the country," state news agency IRNA quoted the health ministry's Minoo Mohraz as saying.
"Since those infected in Qom had no contact with the Chinese ... the source is probably Chinese workers who work in Qom and have travelled to China," she added.
But the official did not provide any evidence to support her claim, and it has not been reported elsewhere in Iranian media.
All of those who lost their lives are believed to be Iranian citizens.
Qom is a centre for Islamic studies and pilgrims, attracting scholars from Iran and beyond.
Following the announcement of the deaths, neighbouring Iraq on Thursday clamped down on travel to and from the Islamic republic.
The Iraqi health ministry announced that people in Iran were barred from entering the country "until further notice".
Kuwait's national carrier Kuwait Airways also announced it would suspend all flights to Iran.