Ukrainian President Volodymyr Zelensky's party is set to convincingly win a snap parliamentary elect
Ukraine election: President Zelensky's party triumphs
Exit polls suggest the Servant of the People party will have a majority in parliament - but will need a coalition partner to form a government.
Mr Zelensky triumphed April's presidential poll - but has been unable to appoint the ministers he wants.
He has pledged to implement radical reforms and tackle rampant corruption.
Speaking outside a polling station after casting his ballot in Kiev earlier on Sunday, Mr Zelensky told that the snap election was "maybe more important than the presidential election".
Polling stations across Ukraine closed at 20:00 local time (17:00 GMT), and first official results are expected within several hours.
What do exit polls say?
They say the Servant of the People will have about 44 percent of the vote, far more than each of the other four parties predicted to have cleared the 5 percent threshold to enter parliament.
Speaking in Kiev after the polls closed, President Zelensky said he was inviting a party led by rock star Svyatoslav Vakarchuk to hold talks on forming a coalition.
"This was my initiative even before the election," Mr Zelensky said.
Mr Vakarchuk's Holos (The Voice) party is projected to win about 6 percent of the vote.
The pro-Russian Opposition Platform - For Life party is currently in second place with about 12 percent of the vote. However, Mr Zelensky has ruled out any coalition with it.
The other two parties projected to enter parliament are former President Petro Poroshenko's European Solidarity (about 9%) and Batkivshchyna (Fatherland) led by former Prime Minister Yulia Tymoshenko (about 8 percent).
Mr Zelensky needs support from the Verkhovna Rada, Ukraine's parliament. The victorious party or coalition will form a government and nominate a prime minister.
The president told our correspondent that the "president, prime minister and parliament have to work together, just to make life happy for Ukraine".
He said the key issues were investment, democracy and safety.