KIEV (AFP) - Ukraine's defiant pilot Nadiya Savchenko sang the national anthem on Tuesday (May 31) in a strident first appearance in Parliament since her release in a prisoner swop with Russia last week.

The 35-year-old member of former prime minister Yulia Tymoshenko's populist party strode to the podium draped in the flag of Ukraine and holding one of Crimea - annexed by Russia in March 2014 - at the opening of an emotional session.

Ms Savchenko has turned into a national symbol of resistance to Russia since joining a volunteer battalion fighting pro-Kremlin eastern separatist insurgents and then being taken prisoner in June 2014.

She then mysteriously turned up in a Russian detention centre and was sentenced to 22 years behind bars for her alleged role in the murder of two Moscow state television journalists covering the war.

Her release in exchange for two purported members of Russia's military intelligence service who were captured during a May 2015 battle came after months of international negotiations and was celebrated in the West.

During her detention, Ms Savchenko was elected in absentia to Ukraine's Parliament.

She also staged a series of prolonged hunger strikes - which were dismissed on Tuesday by Russian Foreign Minister Sergei Lavrov as a staged act.

"She is a rather peculiar lady and, by the way, fairly plump," he said in an online questions-and-answer session with one of Russia's most popular dailies.

"So all those hysterics about her hunger strike - I think now everyone understands what they were worth."

But some analysts say Ms Savchenko may yet become a thorn-in-the-side for President Petro Poroshenko because of her political ambitions and high esteem among soldiers still fighting in the former Soviet republic's 25-month war.

Savchenko has already floated the possibility of one day running for president and gave a hint of the trouble she may cause other members of parliament - some of them tainted by links to powerful business interests - in her opening address.

"I have returned and I will not let you forget - you, the people who sit in these armchairs in parliament - about the boys who began laying down their lives for Ukraine on Maidan Square and continue dying today in the east," she said.

Ukraine's bloody Euromaidan Revolution of February 2014 toppled an unpopular Moscow-backed leadership and opened the door to stronger ties with the West.

Some of the most prominent of the leaders of those historic days have since expressed disenchantment with Mr Poroshenko's seeming inability to eliminate decades of cronyism and back-room dealings from Ukrainian politics.

One of Ms Savchenko's first acts as deputy was to tear down a banner bearing her name and picture that had hung from the parliament's rostrum for months.

She also intimated a possible leading role in the struggle to rid the nation of the corruption that drove many to join the 2014 pro-EU revolt.

"I want to tell you that nothing is forgotten, no one is forgotten, and no one is forgiven," Ms Savchenko said firmly.

"The people of Ukraine will not let us sit here if we betray them," she added in a veiled warning of another popular revolt.

Parliament speaker Andriy Parubiy praised Ms Savchenko for being "one of the irreplaceable symbols of Ukraine at a time when Ukraine was on fire".

Other lawmakers stood and applauded as Ms Savchenko approached the podium in a short-sleeved white shirt.