Armenian officials say 75 were injured and more than 20 detained in clashes between riot police and protesters in the capital.

The unrest erupted late on July 29 in Yerevan when demonstrators tried to approach a police station where gunmen from an opposition group have barricaded themselves.

The violence, which left three RFE/RL journalists injured, unfolded amid the sound of gunshots and explosions coming from the compound located in the city’s southern Erebuni district. It was not immediately clear whether security forces were conducting a large-scale operation there.

The protesters sympathetic to the gunmen unexpectedly tried to approach the building from the nearby Sari Tagh neighborhood overlooking it. Some of them threw stones when they were confronted by rows of riot police, who briefly fired stun grenades in response.

The chief of Yerevan’s police department, Ashot Karapetian, and other senior law-enforcement officers warned two protest leaders -- Amen Martirosian and Levon Barseghian -- that they must lead the crowd back to the city center.

“Armen, you can’t control them,” said Karapetian. “They threw stones. Some policemen were injured. Tell the people to go back to where you held rallies [until now.]”

Martirosian said the stones were thrown by “provocateurs” and assured the officers that the crowd did not intend to break through the police cordon and enter the police compound.

The officers dismissed the assurances. They said that the rally was illegal and that gunshots fired around the compound were too dangerous for its participants.

About 10 minutes later, the police charged at the protesters, firing tear gas and throwing stun and flash grenades.

Some protesters as well as three RFE/RL journalists -- Karlen Aslanian, Hovannes Movsisian, and Garik Harutiunian -- were attacked and beaten up by a large group of plainclothes men armed with sticks and metal bars as they retreated towards downtown Yerevan. The men, who appeared to be police officers, were clearly aware that they were assaulting reporters.

“Are you filming?” one of them said before punching Movsisian, smashing his camera and tearing off his ID badge.

“I told them that I stopped filming but they kept hitting me,” Movsisian said by phone as he ran for safety and took cover in a local shop shortly before midnight.

“They are chasing us and trying to arrest everyone in sight,” he said, adding that he witnessed dozens of protesters injured and detained at the scene.

WATCH: Fresh Clashes In Yerevan (natural sound)

The two other RFE/RL reporters were also injured before fleeing to safety through another Sari Tagh street.

At about the same time, the police also dispersed a smaller crowd that gathered on a section of Khorenatsi Street leading to the seized police building. The street section has been the scene of rallies held nearly every day in support of the gunmen.

The police used force moments after a senior officer told 200 or so people standing there that their gathering was illegal. Dozens of protesters were subsequently detained.

One young man had blood all over his face as he was dragged away by several officers. The officers claimed that he fell to the ground and injured himself before being caught.

The police did not attack journalists or obstruct their work in that area.

Another RFE/RL correspondent saw seven people rushed to the Erebuni Medical Center, the nearest hospital, more than an hour after the outbreak of the violence. Four of them were injured policemen. It was not immediately clear who the three others were.

“A police serviceman suffered a gunshot wound outside the [Erebuni] police compound and was transferred to hospital,” Armenian police spokesman Ashot Aharonian wrote on Facebook at midnight. He did not say who shot the officer.

At least 20 injured protesters were taken to another Yerevan hospital, Surb Grigor Lusavorich. A senior doctor there told RFE/RL’s Armenian service that most of them suffered burns apparently caused by police stun grenades. Two of them are in serious condition, he said.

Meanwhile, Aharonian defended the use of force at Sari Tagh. He claimed that the protesters tried to join the besieged gunmen from that neighborhood.

In a Facebook post, Aharonian insisted that security forces were “not conducting any operation” against the armed oppositionists.

Aharonian promised that the police would “immediately” investigate violent attacks on journalists from RFE/RL and other media outlets that covered the dramatic events.

The Armenian Human Rights Ombudsman’s office said they were investigating reports that those who attacked the journalists were policemen dressed in plain clothes.

"Radio Free Europe/Radio Liberty is outraged by this attack on journalists carrying out their professional duty," said RFE/RL President Thomas Kent. "We expect the Armenian authorities to bring the attackers to justice and protect journalists carrying out their legitimate work."