Armenia's security forces say armed supporters of a jailed opposition leader are still holding five policemen hostage a day after attacking a police station in the capital and killing one officer and wounding four others.

The National Security Service said in Monday's statement that one of the officers held hostage and also an ambulance driver were freed overnight as a result of prolonged negotiations and undefined "special measures."

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. His group has called for the government of the former Soviet republic to step down.