The leader of a right-wing party has been questioned in connection with Monday's clashes outside the Ukrainian parliament on Kiev.

Three National Guard officers died from injuries suffered in a grenade explosion during clashes between police and nationalists who were protesting a constitutional amendment granting more powers to Ukrainian regions including the rebel-held east.

Svoboda leader Oleh Tyahnybok turned up for questioning at the Interior Ministry on Friday. Tyahnybok is officially a witness while 16 Svoboda members have been arrested on suspicion of orchestrating the riots.

Most of the 100 violent protesters at Monday's rally outside the parliament were members of Svoboda, which holds only a handful of seats in parliament. Wielding truncheons and sticks with nails, they faced off against police in riot gear.