Tehran, Iran - In the busy Enghelab Square in central Tehran, a sheen of normality prevails as residents go about their business like any other day - if not for the large number of security personnel interspersed throughout this bustling part of the Iranian capital.

Over the past four nights, the square has become a key gathering point for protesters chanting anti-establishment slogans, part of a wider wave of rallies sweeping Iran since last week.

The square has seen skirmishes break out in recent evenings, with police using tear gas and water cannon to disperse protesters.

On Tuesday morning, business went on as usual in the area, a popular destination for literature lovers due to its many bookstores.

However, with online statements calling for fresh protests in the evening, business owners remain cautious.

"We need to be careful," Reza, a 31-year-old owner of a small store selling books and stationery products, tells Al Jazeera.

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"Business is normal during the day, but we have had to close the store earlier in the past few days," he adds.

At least 22 people have been killed since protests erupted on Thursday in Iran's second-largest, eastern city of Mashhad, before spreading to other parts of the country.

Initially, the anger of the protesters was directed towards the economic policies of the government led by President Hassan Rouhani.

Soon, however, the grievances turned political, with protesters chanting slogans against the establishment and the ruling religious elite.

In the capital, no casualties have been reported so far. However, police have arrested more than 450 protesters during the past three days, according to Ali Asghar Naserbakht, the deputy governor of Tehran province.

More than 100 people were arrested on Monday alone, Naserbakht told ILNA news agency.

Authorities insist that the situation in Tehran is under control - the Iranian Revolutionary Guard Corps (IRGC), who are in charge of providing security in Tehran, have repeatedly stressed this.

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"The protests are smaller than they need to be for the IRGC to intervene," Ramezan Sharif, a spokesperson for the forces, has been quoted as saying by Iranian media.

However, concerns about the effect of the unrest have also extended to the business sector. On Sunday, a 1.7 percent drop at the Tehran Stock Exchange spooked investors.

The fall came after equity markets had recorded an all-time high in late November.

"Until recently, companies were increasing their capital and expanding their business," Mohammad Sharifi, a stock investor and economics graduate of Tehran University, told Al Jazeera.

"I lost 10 percent of my investment after the fall in equity index on Sunday."

The losses did not prevail, as markets recorded some gains on Monday and Tuesday, but a depreciation in the value of the Iranian rial has created further anxiety.

Since the rallies broke out, the rial has depreciated more than seven percent against the euro, while the US dollar has also risen 2.8 percent in the Iranian market.

This could have an effect on the livelihood of middle-class Iranians.

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Many expat students who have returned to Tehran to visit relatives during the winter holidays are now anxious.

Speaking to Al Jazeera, some said they were surprised to see currency exchange stores refusing to sell them foreign cash as they wait for markets to stabilise.

Back in Enghelab Square, life seems to carry on as normal. However, Reza, the bookstore owner, says he will take no chances and close his shop early.

"It gets tense in the evening."