One of the gunmen locked in a two-week stand-off in a police station in the Armenian capital Yerevan shot an officer dead on Saturday, a police spokesman said.
"A sniper opened fire from inside the police station and killed a police officer ... who was sitting in a car parked 350-400 metres (yards) away," Ashot Aharonyan wrote on Facebook.
Armenia's security services issued an ultimatum to gunmen holding up Erebuni police station Saturday, in a bid to resolve a weeks-long hostage crisis after dozens were hurt in overnight clashes.
"We are giving members of the armed group until 17:00 (1300 GMT) to lay down their arms and surrender," the Armenian national security services said in a statement.
"Otherwise special forces law-enforcement have the right to open fire," it said. "After the events of July 29, any opportunities to resolve the situation with the terrorists peacefully have been exhausted."
"Out of 73 injured people, 26 are still in hospital, including six policemen," health ministry spokeswoman Anahit Haytayan wrote on Facebook.
Hundreds of protesters who support an armed pro-opposition group clashed with Armenian police Friday night in Yerevan.
By Saturday, dozens were injured and 26 arrested after authorities broke up a rally near the police station, where the armed pro-opposition group has been holed up for almost two weeks with several hostages. Police used batons, stun grenades and smoke bombs to break up the demonstration in support of the gunmen, who are still holding two medics. Officers charged at protesters shouting "Free independent Armenia".
Journalists were among those hurt and a house caught on fire in the neighbourhood. US-based Radio Liberty said three of its journalists were among the injured.
Armenian police told AFP that 165 people were detained in total during the unrest, of whom 26 were later arrested. The rest were released.
Authorities said they have launched a criminal probe into 23 of the protesters, including a member of the pro-Western Heritage party Armen Martirosyan.
However, the Armenian Ombudsman accused police of heavy-handed tactics against journalists during the protest, and said plain-clothes officers prevented media from covering the event.
On July 17, an armed group stormed Erebuni police compound in Yerevan and killed a police officer and took hostages. Some of the hostages have been released.
The gunmen – supporters of fringe jailed opposition leader Zhirair Sefilyan – also seized a store of weapons.
They have since freed all the police but on Wednesday seized four medical staff who had entered the compound to treat some of their wounds, two of whom were later released.
Around 24 gunmen are still inside.
According to CivilNet news broadcast, the armed group identified itself as the Daredevils of Sassoun.
The group's name refers to an Armenian epic poem inspired by the struggle of four generations of Sassoun's warriors against Arab rule from 8CE to 10 CE.
The group released a video that seeks the release of “political prisoners” including Sefilian and called people to take part onto the streets.
The group also said it will retaliate if attacked and has no intention of surrendering. It demanded the resignation of President Serzh Sarkisian and Sefilyan's release. Protesters have regularly gathered in the neighbourhood, voicing similar calls, chanting “Serzh, leave!”.
During the protests, police threw grenades, tear gas batons and sound bombs against the protesters.
— Agnia Grigas (@AgniaGrigas) July 30, 2016
Sefilian, the leader of a small opposition group called the New Armenia Public Salvation Front, is a former military commander, and a critic of the government over the disputed territory of Nagorno-Karabakh, a dispute which started following the end of the Soviet Union.
He and six followers were arrested in June after they were accused of preparing to take over government buildings and telecoms facilities in the capital Yerevan.
Yerevan-based journalist, Maria Titizian, told Al Jazeera, “People will resort to violence when they feel the system has failed them.”