Right Sector spokesman Artyom Skoropadskyi said that "if necessary," the organization would bring fighters to Ukraine's capital if the standoff continues.
The conflict between Ukraine's internal ministry and the nationalist Right Sector group began on Saturday after a conflict around cigarette smuggling turned into a deadly shootout with nearly a dozen wounded, including civilians. Right Sector and Ukraine's Interior Ministry accuse each other of firing the first shots. Ukraine's Security Service (SBU) said that it will not negotiate with the group.
"If necessary, we can send the reserve battalions anywhere we want. We can send all reserve battalions to the Presidential Administration an the Internal Affairs Ministry," he said.
Skoropadskyi added that given the group's size, it would not need to remove its fighters from the Donbass, where the group is taking part in the Ukrainian military operation against Donbass independence supporters.
The group also began picketing Ukrainian police headquarters around the country, calling for the removal of internal minister Arsen Avakov.
Right Sector leader Dmytro Yarosh was appointed to be an advisor to the country's military in April, when his group was also legally formalized.
Ukrainian President Petro Poroshenko has not yet issued any statements on the incident.