Thousands of Ukrainians marched in Kiev on Monday, decrying as "capitulation" a mooted pullback of troops fighting Moscow-backed separatists in the east and calling for victory in the five-year war.
The protesters, many veterans of the conflict in eastern Ukraine, paraded through the centre of the capital with flares burning, singing the national anthem and chanting slogans against President Volodymyr Zelensky.
It was the second of two marches in Kiev on Monday, a national holiday designated "Defenders Day". Demonstrators later gathered on Kiev's Independence Square.
October 14 also marks the anniversary of the foundation of the Ukrainian Insurgent Army (UPA), a group of nationalists who fought against Soviet troops in World War II alongside Nazi forces, and are accused of slaughtering Poles and Jews.
Nationalist forces traditionally hold marches on this day, including supporters of the Svoboda party.
Police said abound 12,000 people participated in the march, and some 6,000 in the earlier event.
Protesters chanted "No to capitulation!", "Ukraine above all" and "Russian language today, Russian tanks tomorrow".
Some 10,000 people including Ukraine's former president Petro Poroshenko had demonstrated earlier this month against a plan for broader autonomy for separatist territories ahead of a high-stakes summit with Russian leader Vladimir Putin.
Zelensky on Monday visited troops in the war-ravaged eastern Donetsk region and met commanders and servicemen.
He called the 2014 Crimea annexation and the conflict with separatists Ukraine's "moments of truth".
Zelensky said in a speech that a nation faced two choices in such moments, "to surrender and disappear from the face of the Earth, or to be born the second time."
He is pushing for Western-mediated talks with Putin in Paris in an effort to revive a stalled peace process.
But those efforts have stalled as Kiev forces and separatist fighters have so far failed to pull back troops along the frontline.
In the run-up to the summit, negotiators agreed a roadmap that envisages special status for separatist territories if they conduct free and fair elections under the Ukrainian constitution.
But critics say the proposal favours Russia.
- 'Get back our lands' -
Protesters in Kiev said they saw any summit with Putin as a loss for Ukraine.
"Already I feel that we are giving up our national interests," said writer Nataliya Tysovska.
"If we pull back our troops again there will be a giant 'grey' zone that will be occupied by someone else."
"The current government is taking steps that could lead to the capitulation of Ukraine as a whole," Oleksiy Kaida, deputy head of the Svoboda nationalist party, told AFP.
"We have to get back our lands at any price: not just Donbass but also Crimea," he said.
The conflict has become the worst East-West crisis since the end of the Cold War and claimed some 13,000 lives.
Ukraine has seen a rise in nationalism since the ouster of Kremlin-backed leader Viktor Yanukovych in 2014 led to the annexation of Crimea.