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When state-owned Ukrainian TV broadcast celebrations of Russia's annexation of Crimea on Moscow's Red Square, a group of nationalist politicians cried betrayal. They burst into the office of the channel's executive, accused him of being a Russian stooge, punched him and forced him to sign a resignation letter.

The assault, which prompted condemnation in the West, presents an important test for Ukraine's new pro-Western government.

First, it's eager to show a modern, democratic face to the world as it enters a landmark political association pact with the European Union. Perhaps more gravely, the nationalist violence plays directly into the hands of Russia's propaganda spinners: State-controlled media eagerly used the incident to portray Kiev's leadership as a hive of radical nationalists who terrorize Russian speakers, justifying the Kremlin's moves to protect them in Ukraine.

Tensions are high in Ukraine as the government debates whether to pull its troops from the Crimean peninsula, where Russian forces are seizing Ukrainian ships and evicting soldiers from military bases. Crimeans are eagerly lining up to apply for Russian passports, while Russian tanks and troops amass near the border with eastern Ukraine.

For Ihor Miroshnichenko, a lawmaker with the nationalist Svoboda party, those scenes of Russian domination were all too much.

And the broadcast of Russian celebrations seemed to add insult to injury.

To vent his rage, he led a group of Svoboda colleagues in storming the office of the First National channel's chief, Oleksandr Panteleymonov, used an insulting term used to describe Russians and punched him repeatedly, while an aide recorded the scene on video.

"Today Ukraine is in a state of war and in a state of partial occupation by Russia. And when war is going on, giving the air to the enemy — I believe it is state treason," Miroshenichenko, a former journalist who sits on the parliamentary committee on freedom of speech, told the Hromadske online television channel.

"I cannot imagine that Poland which was occupied by Hitler would give him airtime on the radio so that Fuhrer could explain his position."

Miroshnichenko admitted that he may have overreacted — although he refused to acknowledge that he actually beat Panteleymonov.

The TV executive said in a statement Friday that he is ready to leave his post, but only if there is a legitimate government decision to replace him.

Prime Minister Arseniy Yatsenyuk condemned the assault as undemocratic.

"These are not our methods," Yatsenyuk said in a statement. "A country which is going toward the European Union will continue to profess the basic principles and values of the European Community."

His position is complicated by the fact that Svoboda, a vocal force in parliament that took part in the protests that ousted the pro-Russian government, received several key posts in the Cabinet — including prosecutor general, the very figure who will be in charge of investigating the TV station attack.

The United States said it was "deeply offended by this incident, which was not an exercise in patriotism, but instead a reminder of the thug-like tactics previously employed by the Yanukovych regime," the U.S. Embassy in Kiev said in a statement. "This behavior has no place in a Ukraine committed to defending democracy, civil liberties, and individual freedoms, particularly press freedoms."

Global rights watchdog Amnesty International also denounced Svoboda's actions, calling on the government to "waste no time in demonstrating that basic human rights are protected in Ukraine and that nobody will face discrimination because of their political views or ethnic origin."

Several dozen activists picketed the prosecutor's office this week, protesting the incident and calling for an honest probe of Svoboda's actions.

Meanwhile, Russian media were quick to spot an opportunity. They prominently played the Miroshenkichenko video on state television, calling Svoboda activists "bandits" and accusing them of staging a "pogrom" in the channel's offices.

Many in Ukraine noted that by lashing out so violently, Svoboda was handing the Kremlin a PR gift.

Social Ukrainian media showed doctored images ridiculing Miroshnichenko as a Kremlin stooge. One image had Russia's chief propagandist, the TV host Dmitry Kiselyov, pinning an award on Miroshnichenko's chest and thanking him.

Roman Skrypin, the Hromadske anchor who interviewed Miroshnichenko, condemned the nationalist's actions.

"If you don't like a newspaper, you don't read it, if you don't like a TV channel, you turn to a different one," Skrypin said. "What are you doing? You handing the cards into the enemy's hands."