War in east of country visible in makeup of Rada, with dozens of men in fatigues walking the corridors as newly elected MPs

Paramilitary commanders in fatigues, investigative journalists and a fighter pilot absent because she is in a Russian jail are among the members of Ukraine’s new parliament, which sat for the first time on Thursday, reflecting how much the country has changed this year and the formidable challenges it still faces.

The parliament is the result of the first parliamentary elections since the ousting of President Viktor Yanukovych by the Euromaidan protest movement in February. But 27 of its seats remain empty, a sign of the territory lost since the revolution – Crimea annexed by Russia, and parts of the east under the control of Moscow-backed separatists.

As well as activists from Euromaidan and commanders who have led the fight against separatists in the east, the parliament also contains a number of far-right figures, including Dmytro Yarosh, leader of the Right Sector movement, and Andriy Biletsky, who leads the Azov battalion, a volunteer grouping known for its Nazi symbols and far-right ideology.

President Petro Poroshenko said that by electing a new parliament Ukraine would have completed a “total reboot of power”. More than half of the MPs are new to politics, only two of six parties elected existed a year ago and there is no Communist party representation for the first time.

Poroshenko told the Rada, Ukraine’s parliament, the country would always have to sleep “with a revolver under the pillow” given the threat from the east. He spoke by phone with Vladimir Putin on Wednesday, officials in Moscow and Kiev said. Poroshenko’s press service described the call as “constructive”. Kiev accuses Moscow of giving logistical and military support to the rebels it is fighting in the east.

Poroshenko put on a show of unity with the prime minister, Arseniy Yatsenyuk, at the opening of parliament on Thursday. Rivalry between the two men has alarmed western politicians who are keen to see a strong government in Kiev that is able to tackle the myriad of economic and political reforms required.

The effects of the war in east Ukraine were visible in the makeup of the Rada. Instead of police, fighters from several volunteer battalions in shabby uniforms guarded the perimeter, while inside more than a dozen men in fatigues walked the corridors as newly elected MPs. Fighter pilot Nadiya Savchenko, elected as part of a party list, was absent. She is in jail in Russia accused of the death of a Russian journalist. Kiev says she was illegally seized by Russian forces inside Ukraine and dragged across the border.

In a parliament that has long been known for altercations and fistfights, there were fears that the new set of MPs could prove more unruly than ever, especially after the commanders of two volunteer battalions active in the east had promised to solve their personal differences “like men” inside parliament.

But Semen Semenchenko, commander of the Donbas battalion, said it was “not the right time or place” to settle his conflict with the commander of the Aidar battalion. Semenchenko told the Guardian his two main priorities were the fight against Russian forces in the east and the fight against corruption.

“Previous parliaments could not achieve this, but I am determined that this old system will not defeat us,” he said.

The remnants of former ruling Party of Regions, for years the dominant force in Ukrainian politics, have been renamed the Opposition Bloc. It is now the smallest faction in parliament. The new coalition will be formed by five pro-western parties. They have already prepared an agreement that outlines 17 vital reforms the country needs to undertake to avoid economic disaster and restore security.

After opening the session the MPs read out their oath and observed a minute of silence to remember the activists killed during the revolution, as well as Ukrainian soldiers and civilians killed during hostilities in the east. In the afternoon the MPs chose former the deputy prime minister Volodymyr Groysman as speaker, officially formed the parliamentary coalition of five parties and re-appointed Yatseniuk as prime minister.

Poroshenko called on parliament to work to make the country ready to apply for EU membership within five years.