0858 GMT July 23, 2019
A month after scoring a landslide victory against incumbent Petro Poroshenko amid widespread public discontent with the political establishment, the 41-year-old comedian has become Ukraine's youngest post-Soviet president, AFP reported.
"Our first task is a cease-fire in the Donbass," Zelensky said during the ceremony in parliament in Kiev, referring to the eastern region, prompting a round of applause.
"We didn't start this war but it is up to us to end it," he said.
He also did not recognize Crimea’s reunification with Russia after a referendum in March 2014, saying, "Crimea and Donbass are Ukrainian land".
Zelensky added that Ukraine had lost not just territory but the hearts and minds of people living there, who "are not strangers, they are ours, Ukrainians."
He also announced that he would dissolve parliament, in order to call early parliamentary elections, which had originally been scheduled for October.
"People must come to power who will serve the public," Zelensky said after wrangling with hostile lawmakers whom he has called "petty crooks."
Critics had questioned whether Zelensky would be able to govern without a parliamentary majority. Even setting a date for his inauguration took weeks of negotiations with lawmakers.
In a hard-hitting speech, Zelensky called for the sacking of the head of the state security service, prosecutor general and defense minister – which has to be approved by parliament.
Defense Minister Stepan Poltorak and Head of the Security Service of Ukraine Vasyl Grytsak swiftly tendered their resignations.
High fives outside parliament
Zelensky took a non-traditional route to his inauguration – walking on foot from his home nearby, after saying he wanted a less pompous ceremony.
Dressed in a dark suit, he exchanged high fives with supporters waiting outside, took selfies with them and even jumped up planting a kiss on a supporter's forehead.
In his speech, Zelensky referred to his background as a comedian. "In my life, I've tried to do all I could to make Ukrainians smile," he said.
"In the next five years I'll do all I can so that Ukrainians don't cry."
When the actor and comedian announced his candidacy on December 31, few took it seriously, but after an unprecedented campaign largely waged through social media, he won more than 73 percent in the second round on April 21, trouncing Poroshenko.
Poroshenko led Ukraine for five years, overseeing the fallout over Crimea and the conflict in the east.
Though he launched some reforms, he was criticized for failing to improve living standards or effectively fight corruption.
Kremlin spokesman Dmitry Peskov on Monday said Russian President Vladimir Putin has no plans to meet with Zelensky and would not be congratulating him on taking up the post.
The Russian president will instead "congratulate him on the first successes" in regulating the conflict, he said, calling it a "domestic problem" for Ukraine.