Most merchants in Tehran’s grand bazaar reopened for business Thursday as an unusually large number of police officers were deployed around the city’s black-market money trading district, witnesses reported. The reopening came a day after a crackdown on suspected speculators led to civil disturbances and a large protest march by Iranians demanding relief from the plummeting value of the currency, the rial.

Iran’s Fars news agency reported that 16 people, described as ‘‘elements of disorder in the currency market,’’ were arrested during the protests, the first outbreak of anger over the devalued rial and other acute economic problems that have been building in Iran for the past few years.

Economists have attributed the problems to government mismanagement and Western sanctions imposed on Iran in response to its contentious nuclear program, most notably a severe restriction on the country’s ability to sell oil and its expulsion from the global banking network.

Witnesses in Tehran said there was no resumption of protests over the rial, which had fallen by about 40 percent since last week and had contributed to panic selling on the black market by worried Iranians. But there were also no black-market transactions in Tehran on Thursday, as traders and their prospective customers stayed away after having been scattered by riot police officers on Wednesday.

Fars quoted the Tehran prosecutor’s office as saying the 16 suspects had been charged with ‘‘extensive exchange of hard currency beyond the banking system; of buying, selling, and smuggling hard currency; forming organized gangs; making fake and unreal currency deals in order to increase the price of hard currency and to disturb public order and disrupt trade and bazaar; and gaining illegal capital by the aforementioned actions.’’

As a result, the prosecutor’s office was quoted as saying, foreign currency values had spiked against the rial to unreasonable levels and the suspects had caused a ‘‘severe violation of people’s rights.’’

There was no word on the identity of the suspects. Iran’s Mehr news agency reported Wednesday that two Europeans were among those arrested.

Political economists have called Wednesday’s protest a harbinger, particularly if the politically powerful merchant class in Iran loses confidence in the government. But there have been no public demands for the government to be more flexible over the nuclear issue, which could lead to an easing of the West’s antinuclear sanctions.

President Mahmoud ­Ahmadinejad and other Iranian leaders have called the sanctions the equivalent of blackmail and have vowed to never capitulate on what they call Iran’s right to peaceful uranium enrichment.

Western powers say they suspect Iran’s real purpose in uranium enrichment is to ­develop the ability to make ­nuclear weapons.

The possibility of further sanctions over the nuclear issue advanced Thursday in Europe, where diplomats said European Union foreign ministers could impose new limits on Iranian gas exports during a meeting in Luxembourg on Oct. 15.

An EU embargo on Iran oil that took effect in July has played a large role in severely restricting Iran’s ability to sell oil, its most important export.