The Iranian authorities publicly hanged on Tuesday two participants in the country’s widespread January protests, human rights groups said, the latest executions in what activists describe as a rapid increase in the government’s use of the death penalty this year.

The hangings were carried out at dawn in Isfahan’s Shahid Alikhani Square, according to the Washington-based Human Rights Activists News Agency, and appeared to draw a rare public backlash.

Several videos verified by The New York Times show large crowds of chanting protesters near the site. Blurry footage circulating on Telegram and social media early on Tuesday morning in Iran showed protesters around the corner from the square, chanting “shameless” and booing.

Iran has long been one of the world’s most frequent users of capital punishment, but public executions are extremely rare. Several human rights activists described Tuesday’s hangings as an escalation by a government seeking to stifle dissent after the unrest in January, particularly during the war with the United States.

Mahmood Amiry-Moghaddam, director of the Norwegian-based Iran Human Rights group, called the executions “a brutal form of state terror that the international community must not tolerate.”He said, “Public executions are among the regime’s most potent instruments for instilling fear and fostering a sense of helplessness among the public.”

The two men executed on Tuesday were Amirhossein Safari and Abolfazl Sepahi, according to Mizan, the news agency associated with Iran’s judiciary. Mizan did not mention a public execution, but two other media outlets in Iran described the hangings as being conducted “in the presence of the public.”

The men were part of a group accused by security forces of killing four police officers during protests on the night of Jan. 8. According to an indictment, the assailants attacked the officers with knives, machetes and axes, then doused them with gasoline and set their bodies on fire.

Lawyers representing the two men did not publicly comment on the charges, but both men gave televised confessions broadcast on Iran’s state news channel several months ago. Iranian rights groups and human rights lawyers say such confessions are often made under duress, frequently after psychological or physical torture.

Several human rights groups said that the men, like other protesters sentenced to death after the January demonstrations, had not been given due process.

A report released by Human Rights Activists News Agency, or HRANA, said that lawyers for Mr. Safari and Mr. Sepahi had faced difficulties gaining access to their case files and that the court rejected what could have been exculpatory evidence. The families were kept in the dark about the details of the verdicts, the report said.

According to HRANA, fourteen men have been sentenced to death on charges of involvement in the police officers’ killings, though it identified only 12 of them by name.

The selection of Shahid Alikhani Square for the execution was likely symbolic, because it is where the authorities allege that the four officers were killed, said Hassan Nayeb-Hashem, founder of the Vienna-based All Human Rights for All in Iran.

Saeid Dehghan, an Iranian human rights lawyer based in Toronto, described the event as the government “baring its teeth in an effort to suppress the public.”

Yet several videos appear to show that the hangings had the opposite effect on some people.

In one video, a crowd can be heard booing as the Islamic call to prayer rings out. Another video shows more crowds in a different area on the outskirts of Shahid Alikhani Square. In the footage, shots are heard ringing out, and the person filming begins to run.

Several Iranian-focused rights groups have warned for months that the pace of sentencing and hangings appears to have surged amid the war.

Mahya Ostovar, founder of the Iranian Democratic Diaspora Network in Ireland, said that more than 800 executions had been verified this year. “As the world’s attention has focused on war and diplomacy, the human rights catastrophe inside Iran has only intensified,” she said.

The United States and Israel launched their war against Iran just weeks after security forces crushed nationwide demonstrations. The government says some 3,000 people were killed in the protests, while activist groups like HRANA put the toll above 7,000.

“These executions should also serve as a warning that the real war in Iran has never been the one dominating international headlines,” Ms. Ostovar said. “The real conflict is the ongoing struggle between the Iranian people and the Islamic Republic. That struggle is far from over.”