Several thousand people have marched through the center of the Ukrainian capital to call for President Petro Poroshenko's resignation.
Police said the February 4 demonstration organized by opposition politician Mikheil Saakashvili's Movement of New Forces party attracted 2,500 people, but local reports said up to 5,000 people participated.
Addressing the demonstration, Saakashvili said the event marked the beginning of a campaign to "dismantle this rotten and corrupt system."
"And Poroshenko's resignation is only the first step," he added.
"The people who have ascended to the government in our country do not deliver on people's demands," a protester told RFE/RL, calling for Poroshenko's impeachment and his "whole corrupt government to go away."
The protester said that "nothing has been done from what people called for" during the Euromaidan protests that pushed Moscow-friendly President Viktor Yanukovych out in 2014 and brought Poroshenko to power.
Organizers of the "March for the Future" are also calling for early parliamentary elections and the formation of a new government.
The demonstrators adopted a resolution calling for nationwide rallies on February 18, lawmaker Yuriy Derevyanko said.
The participants in the protest marched from Kyiv's Shevchenko Park to European Square, where they held a rally, holding Ukrainian flags and red-and-black party banners and shouting slogans such as "Resignation" and "Ukraine without oligarchs."
About 2,000 law enforcement officers were deployed to the capital ahead of the rally. No incidents were reported.
Mikheil Saakashvili marches with supporters in Kyiv on February 4.
Saakashvili was president of Georgia from 2004 to 2013. He gave up his Georgian passport in 2015 when he accepted Ukrainian citizenship in order to take the post of Odesa governor at the request of Poroshenko.
Saakashvili resigned from the Odesa post in November 2016, accusing the government of undermining his efforts to fight corruption and carry out reforms, and has since become an ardent opponent of the Ukrainian president.
He was then stripped of his Ukrainian citizenship by Poroshenko in June 2017 in a move he is challenging in court.