Kiev, Ukraine: Two senior members of a Ukrainian nationalist party were charged on Friday with rioting while their leader walked free after being questioned in Kiev in connection with Monday’s clashes outside the parliament.

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. More than 140 people were hospitalised including one officer who is still in a coma.

The police said they had found the man, formerly a fighter in a volunteer battalion in the restive east, who is believed to have thrown the grenade.

Following clashes, another nationalist party walked out of the parliament majority coalition, threatening to tip the already precarious balance of power in Ukraine where a months-long protest swept a pro-Russian president from power in February 2014.

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

“It’s only the current government which is building a dictatorship under the guise of pretty slogans that is benefiting from the tragedy that happened on August 31, 2015, outside the Supreme Rada,” he told reporters before questioning.

The Interior Ministry on Tuesday issued photographs of the protesters facing off the police on Monday, which featured the Svoboda’s two members with a truncheon in one hand and a shield in another.

Investigators have promised a speedy probe, saying that perpetrators and organisers could face lengthy prison sentences as the clashes have been classified as a terrorist attack.

Most of the 100 violent protesters at Monday’s rally were members of Svoboda, who wielded truncheons and sticks with nails as they faced off against police in riot gear.

Meanwhile, Russian President Vladimir Putin on Friday condemned the deadly clashes that took place this week between police and nationalists in Kiev and questioned how long Ukrainians would “put up with” the instability rocking the country.

In his first public comments on the unrest, Putin lamented the “tragic events” that unfolded outside Ukraine’s parliament on Monday after a vote on granting more autonomy to regions including two breakaway pro-Russian regions in the east.

Speaking at an international economic forum in Vladivostok, Putin was quoted by TASS state news agency as saying the violence constituted “the next enactment of the political confrontation in Ukraine”, where the expulsion of a pro-Russian president in 2014 brought a pro-Western government to power.

Asked how he saw events in the former Soviet state unfolding, Putin said: “This doesn’t depend on us, this depends on Ukraine itself, on the Ukrainian people, how long the Ukrainian people will put up with this bacchanalia.”

The constitutional reforms being debated by Kiev’s parliament, which passed a first reading in parliament Monday, are part of a package of reforms required under a February peace deal between Ukraine and pro-Russian rebels in the east who took up arms against Kiev after the February 2014 expulsion of Russian-backed then president Viktor Yanukovych.

Putin said that it was “crucial” to give more powers to the separatist Donetsk and Lugansk regions.

He also urged Ukraine to pass a law on amnesty for combatants.