In the past 24 hours, 13,890 new cases were confirmed across the country, ministry spokeswoman Sima Sadat Lari said in televised remarks.
It is the highest number of daily infections since 4 December and close to the peak of 14,051 positive cases recorded on 28 November.
The Islamic republic is battling the Middle East's deadliest outbreak of the Covid-19 illness and case numbers have risen following a surge in travel during the Iranian new year holidays that started on 21 March.
Tehran is now classified as "red" on the country's coronavirus risk scale, according to the health ministry, with only essential services, such as food providers and health centres, remaining open.
The new reported cases brought the total number of infections to over 1.94 million, Lari said.
Monday's 172 virus fatalities were also at their highest level since 23 December.
Read more: Iran's homemade Covid vaccine '90% effective'
According to Health Minister Saeed Namaki, Iran is now facing "one of the most severe waves of the coronavirus".
"Sadly, no one listened to me about managing travel and today we're facing a great difficulty," he was quoted as saying by the ministry's website.
Follow us on Facebook, Twitter and Instagram to stay connected