A police officer has been shot dead in the Armenian capital, Yerevan, during a stand-off with an armed group holding hostages inside a police station.
It came as police issued a deadline for the anti-government group to surrender.
When the deadline passed, thousands of protesters again took to the streets in support of the group.
Gunmen seized the building nearly two weeks ago seeking the release of "political prisoners" including opposition leader Jirair Sefilian.
Mr Sefilian has strongly criticised President Serge Sarkisian's handling of the Nagorno-Karabakh conflict.
"A sniper opened fire from inside the police station and killed a police officer who was sitting in a car parked 350-400 metres away," police spokesman Ashot Aharonyan wrote on Facebook.
Police issued an ultimatum to the group to surrender following violent scenes late on Friday when police with truncheons and stun grenades clashed with protesters.
About 60 people were injured, including some journalists, and more than 100 arrests were reported..
Armenia's National Security Service said all options to resolve the conflict peacefully had been exhausted and it gave the group until 13:00GMT on Saturday to lay down their arms.
But hours after the deadline passed a crowd of about 5,000 people again rallied in support of the gunmen.
"Bring your relatives and your neighbours on to the streets," shouted protester Albert Bagdassian.
"Our goal is to support the group against which the security services have decided to launch an assault, to march on the street, to paralyse traffic and to show that we are not afraid," he said.
Three gunmen were also wounded on Friday, apparently shot in the legs by police snipers. Two of them were escorted to hospital under armed guard.
The group seized the police station on 17 July, killing one policeman and taking several hostages.
They released a video demanding the release of Mr Sefilian and a number of others, and urging supporters on to the streets.
The CivilNet newspaper identified the group as the Daredevils of Sassoun.
The group has been quoted as saying it will retaliate if attacked and has no intention of surrendering.
Mr Sefilian, a former military commander, has criticised the government's handling of the long-running conflict involving pro-Armenian separatists in the region of Nagorno-Karabakh.
Nagorno-Karabakh lies within Azerbaijan but has an ethnic Armenian majority. A bloody war erupted after the end of Soviet rule in 1988, and there has been frequent unrest since, the latest in April, when clashes left dozens dead.