An armed group with links to a jailed opposition leader has seized a police building in Armenia, killing one officer, taking hostages and demanding that the country’s president resign.

One of the gunmen said on social media that among those taken hostage in the capital, Yerevan, on Sunday was the country’s deputy police chief.

“A group of armed men entered the premises of a police regiment in Yerevan and is holding hostages under the threat of violence,” Armenia’s National Security Service said in a statement. “One policeman was killed and two others wounded. Two of the hostages were freed.”

Nikol Pashinyan, a member of Armenia’s parliament who met the hostage takers, said the group had taken eight police officers hostage but later released one who was suffering from high blood pressure.

“The Armenian state continues to operate normally. Police carry out their duties to protect public order and security,” the security service said, dismissing rumours on social networks that a coup was under way.

Media reports said the group was demanding the release of Zhirair Sefilyan, an opposition politician who was arrested last month for alleged firearms offences.

“We demand the release of Zhirair Sefilyan. We will only obey his orders. Sarkisian must resign,” one of the group members, Varuzhan Avetisyan, wrote on Facebook, referring to the Armenian president, Serzh Sargsyan.

The Armenian president, Serzh Sargsyan. Photograph: David Mdzinarishvili/Reuters

He said that two senior police officers, Armenia’s deputy police chief, Gen Maj Vardan Egiazaryan, and Yerevan’s deputy police chief, Col Valeri Osipyan, were being held hostage.

One of the gunmen, named as Tatul Tamrazyan, was seriously wounded, Avetisyan wrote.

Sefilyan, the leader of a small opposition group, the New Armenia Public Salvation Front, and six of his supporters were arrested in June after authorities claimed they were preparing a plot to seize several government buildings and telecommunications facilities in Yerevan.

A fierce government critic, Sefilyan was arrested in 2006 over calls for “a violent overthrow of the governmnent” and was jailed for 18 months. He was released in 2008.

Last year, Sefilyan and several of his supporters were arrested again on suspicion of preparing a coup but were released shortly afterwards.

A former military officer, Sargsyan has been president of Armenia since winning a vote in 2008 that was followed by violent clashes between police and supporters of the defeated opposition candidate in which 10 people died.