KIEV (Reuters) - Ukrainian servicewoman Nadiya Savchenko, whose resistance to her imprisonment in Russia has made her a national hero and a potentially disruptive force in Ukrainian politics, received a standing ovation in her first address to parliament on Tuesday.

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A helicopter navigator captured while fighting pro-Russian separatists in the Donbass region, Savchenko’s bold defiance at Russian authority during her two-year captivity restored Ukraine’s national pride bruised by the conflict with Russia.

Her popularity became such that Savchenko, 35, was made a lawmaker by opposition leader Yulia Tymoshenko, and upon her release last week, she announced she was willing to run for president, making her a possible thorn in the side of a weakened President Petro Poroshenko.

“I’m back and will not let you forget - you who sit in these seats in parliament - about all those guys, who laid down their lives for the country,” Savchenko said.

“I tell you that nobody is forgotten, nothing is forgotten. Nothing is forgiven. And the Ukrainian people will not let us sit in these seats if we betray them,” she said.

Ukrainians are disappointed in the pro-Western leadership that came to power after street protests ousted a Kremlin-backed president in 2014.

“One gets the impression that lawmakers are like lazy schoolchildren who shirk their work,” Savchenko told reporters after her speech.

A ceasefire brokered between Ukraine and Russia in the east regions is fraying, and the conflict has claimed more than 9,000 lives so far.

After Savchenko’s speech, some lawmakers played down how much influence she could have in the long run.

“Savchenko’s speech scared some people, but far from everyone,” Leonid Kozachenko, a lawmaker in Poroshenko’s faction, told Reuters.

Vadim Rabinovich, an opposition lawmaker, said Savchenko had both positive and negative aspects to her, and that much depended on her relations with Tymoshenko.

“She brings an air of war with her, this is bad. On the other hand, she brings a certain openness, which is good. Let’s wait and see,” he said.

“She and Tymoshenko will have to sort things out first of all. Two lionesses in one cage.”

Savchenko, who had been accused of murdering two Russian journalists, arrived home to scenes of jubilation on Wednesday after her release by Russia in a prisoner swap.

Her handover had been demanded by the West and was cast as a humanitarian gesture by Russian President Vladimir Putin. It came weeks before the European Union decides whether to extend sanctions against Russia imposed over its support of the rebels.