The protesters, who gathered in the Maidan (Independence) Square in Kiev, chanted “No to surrender!,” with some holding placards critical of President Volodymyr Zelensky.
Former Ukrainian president Petro Poroshenko joined the crowd — which numbered at around 10,000 people — as it marched toward the presidential and parliament buildings, Presstv Reported.
Zelensky is preparing a roadmap with clear deadlines to be discussed with the leaders of Russia, Germany, and France for implementing a peace deal in eastern Ukraine.
On September 12, Zelensky said that he hoped the new roadmap would be discussed at a meeting in the so-called “Normandy” format “in the nearest future.”
The protesters claimed that agreeing to give broader autonomy to the regions in eastern Ukraine would mean surrendering the country’s interests.
The 41-year-old president is gearing up to hold his first summit with Russian President Vladimir Putin in an effort to revive a stalled peace process to end the five-year conflict in eastern Ukraine.
The conflict in eastern Ukraine began when a wave of protests in the country overthrew a democratically-elected government and replaced it with a pro-West administration.
That new government then began a crackdown on the mainly ethnic Russians in the east, who in turn took up arms and turned the two regions of Donetsk and Lugansk — collectively known as the Donbass — into self-proclaimed republics.
The war has claimed some 13,000 lives since 2014.
Kiev and its Western allies accuse Moscow of having a hand in the crisis, but Russia denies the allegation.
Just before the conflict began in eastern Ukraine in 2014, the Black Sea peninsula of Crimea, then Ukrainian territory, held a referendum to join Russia. More than 90 percent of the participants in the referendum voted in favor of that unification.