A police officer has been shot dead by armed men locked in a protracted siege with security forces in the capital of Armenia, Yerevan, hours after authorities issued an ultimatum to resolve a weeks-long hostage drama.

"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," police spokesman Ashot Aharonyan wrote on Facebook on Saturday.

The gunmen - supporters of fringe jailed opposition leader Zhirair Sefilyan - stormed the police building on July 17, killing one officer, taking several more hostage and seizing a store of weapons.

OPINION: Armenian hostage standoff and political implications

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 medics were later released.

Earlier on Saturday, Armenia's security services had given the gunmen a deadline to surrender after dozens were hurt and arrested in overnight clashes.



"We are giving members of the armed group until 5pm (13:00 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."

At least 26 people were arrested in the early hours of Saturday after authorities broke up a rally near the police station, where the armed pro-opposition group has been holed up.

More than 70 people were taken to various hospitals around the capital to be treated for wounds, including burns and broken limbs.

"Out of 73 injured people, 26 are still in hospital, including six policemen," health ministry spokeswoman Anahit Haytayan wrote on Facebook.



Police used truncheons, stun grenades and smoke bombs to break up the demonstration in support of the gunmen.

Journalists were among those hurt and a house caught on fire in the neighbourhood, a residential area.

Armenia hostage standoff: Clashes erupt in Yerevan

Armenian police told the AFP news agency that 165 people were detained in total during the overnight unrest, of whom 26 were later arrested.





The rest were released.

Earlier on Friday, police had exchanged fire with the gunmen, wounding two of them, who were then taken to hospital under armed guard.

The group has demanded the resignation of President Serzh Sarkisian and Sefilyan's release and protesters have regularly gathered in the neighbourhood, voicing similar calls.

Sefilyan and six of his supporters were arrested in June, accused of preparing to seize government buildings and telecoms facilities.

READ MORE: Armenia protesters, police clash over hostage crisis

The hostage crisis and violence has shaken the small landlocked ex-Soviet nation, just months after a surge in conflict with Azerbaijan over separatist ethnic-Armenian region of Nagorny-Karabakh left 110 people dead in April.

The US embassy in Yerevan said in a statement it was "deeply concerned by the shocking images and credible reports of violence and excessive use of force by the police to disperse protestors."



"We urge the Armenian government to take immediate steps to prevent a repeat of last night's actions," the embassy added.

Yesterday's serious injuries, today's police death reinforce need for end to violence, peaceful resolution B4 more hurt or killed #Erebuni — US Embassy, Armenia (@usembarmenia) July 30, 2016



The European Union also called for an end to the stand-off.



"Use of force and violence to achieve political change are not acceptable," an EU spokesman said in a statement.



"Conflicts need to be resolved through political dialogue with a respect for democracy, rule of law and fundamental freedoms."