A Ukrainian far-right group demanded the resignation of the interior minister and said it would block roads around Kiev on Sunday in a standoff over a fatal gun battle that challenges the authority of the government.

Kiev has called on Right Sector, which played a prominent role in protests that toppled Moscow-backed President Viktor Yanukovich a year ago, to lay down their weapons after a shootout on Saturday in the town of Mukacheve killed at least two people.

The cause of the violence is not clear. The sides have different versions of events but Right Sector's response underlines the problems Kiev has keeping order while trying to carry out reforms and crush a rebellion in its east.