As Iran struggles to battle the spread of deadly coronavirus, the United States on Thursday heaped more economic pressure on the country by slapping a fresh round of sanctions on more than a dozen Iranian individuals and five companies, al Jazeera reported.

Coronavirus, also known as Covid-19, has killed at least 2,234 people in Iran and the number of confirmed cases infected in the country is approaching 30,000, according to Johns Hopkins University. 

The U.S. Treasury sanctions were announced one day after the family of retired FBI agent Robert Levinson, who went missing more than a decade ago, claimed they believed he had died while in custody in Iran, citing information from U.S. officials. 

Iran's Foreign Ministry spokesman said on Thursday that Levinson had left Iran "years ago" for an unspecified destination.

The new sanctions were announced two days after UN High Commissioner for Human Rights Michelle Bachelet called for sanctions against countries such as Iran to be rolled back to allow their medical systems to fight the virus and limit its spread.

 In a post on his Twitter page on Sunday, Foreign Minister Mohammad Javad Zarif said the "U.S. is not listening" to "the growing global campaign" to lift "illegal" sanctions on the Iranians and thereby "impeding global fight against Covid-19". Zarif suggested "the only remedy" to this intransigence is to "defy the U.S. mass punishment" of the Iranian citizens who are wrestling with the coronavirus pandemic.

Earlier this month, Tehran asked the International Monetary Fund for $5bn in emergency funding to fight the outbreak.

The U.S. "maximum pressure" campaign of successive rounds of sanctions kicked off in 2018 after President Donald Trump unilaterally withdrew from the UN-endorsed 2015 nuclear deal, officially known as the Joint Comprehensive Plan of Action (JCPOA).

The sanctions imposed by the U.S. Treasury on Thursday targeted companies and individuals involved in the construction and maritime services industries.