Security was reinforced in Armenian capital Yerevan, as armed men seized a police station and hostages on Sunday (July 17).
The men were demanding Armenians take to the streets to press their demands for the release of opposition politicians they said had been jailed unfairly.
One of their main demands was to free Jirair Sefilian, an opposition politician whom the authorities have accused of plotting civil unrest.
Sefilian was jailed in June over allegations of illegally possessing weapons.
Armenia's security service said one policeman had been killed and two wounded in the violence, but that negotiations were underway to resolve the standoff peacefully.
Two hostages had been freed, it said. Armenian news agencies cited police sources as saying several hostages remained.