YEREVAN, Armenia (AP) — A standoff in Armenia's capital went into a second day with armed supporters of a jailed opposition leader still holding five policemen hostage on Monday, a day after they killed one officer and wounded four others in an attack on a police station, the National Security Service said.

But one other officer held hostage and also an ambulance driver were freed as a result of "prolonged negotiations" and undefined "special measures," the security service said in a statement.

More than 20 armed men took over the police station in Yerevan on Sunday to demand the release of Jirair Sefilian, who was arrested last month.

Sefilian, a leader of the opposition group Founding Parliament, was charged with illegal acquisition and possession of weapons. Investigators claimed he and his supporters were planning to seize government buildings and the television transmission tower.

His group has long called on Armenians to take to the streets to force the government of the former Soviet republic to step down.

Several hundred supporters gathered Monday evening on Freedom Square in central Yerevan and planned to march to the police station on the edge of town, but they were stopped by police and minor clashes broke out.

In the end, the opposition supporters reached an agreement with police to hold the march as long as they didn't go to the besieged police station. Up to 2,000 took part in a peaceful march to demand that force not be used against the attackers.

Armenia's deputy police chief, Unan Pogosian, offered reassurances that there were no plans to storm the police station or use force to resolve the standoff.