Ukrainian President Volodomyr Zelenskyy Friday said Ukrainians have been fighting "four times longer than the enemy expected," in a statement posted online.

"Ukrainians are proud people who defend their land and won't give up the tiniest part of this land to the occupier, nor the tiniest part of our freedom," Zelenskyy said.

Zelenskyy said it is impossible to say how many days Ukraine will need to "liberate" its land, "but it's possible and necessary to stress that this day will come and we will win, because we've already achieved a strategic breakthrough and we will continue down this path to victory."

He also spoke about Russian attacks on civilian infrastructure saying, "In many regions of Ukraine there's no power or water supply, no heating. It's a real humanitarian catastrophe. "

Zelenskyy said said that if Russian attacks continue, then sanctions placed on Russia "aren't enough."

"They continue to torture Mariupol and Kharkiv, fire missiles on Lutsk and Ivano-Frankivsk. If all this is still going on it means that sanctions already imposed on Russia are not enough and new tougher measures are urgently needed. Russia has to pay for this terrible war, pay every single day," Zelenskyy said.

The Ukrainian government set up 12 humanitarian corridors, according to Zelenskyy.

"If the other side will break the agreements again, our response will be so strong, that humanitarian corridors will be needed for occupiers themselves," he said.

Russian President Vladimir Putin claimed there have been “certain positive movements” in negotiations with Ukraine, “which are emerging almost daily."

Putin made the remarks in a televised meeting in the Kremlin with Belarus’ leader Alexander Lukashenko.

A third round of talks last week ended without any resolution, although the sides agreed to open humanitarian corridors to allow the evacuation of civilians.

But this week Russia has seemed to make subtle shifts in its demands, which suggest it might be slightly moderating its position in the face of heavy casualties in Ukraine and an unexpectedly intense global backlash.

The Kremlin ahead of the last round of talks announced its conditions for ending the war, saying Ukraine must change its constitution to guarantee it will never join political blocs, interpreted as meaning NATO or the European Union, and it must also recognize Crimea as part of Russia and the independence of the two Russian-controlled separatist regions in eastern Ukraine.

The demands are still maximalist but there was no reference to removing Ukraine’s current government under president Volodymyr Zelenskyy, suggesting the Kremlin may have quietly dropped the goal.

-ABC News' Patrick Reevell

Russia’s general prosecutor’s office has asked a court to declare Facebook’s parent company, Meta, an "extremist organization," a designation that would equate the company with terrorist groups like ISIS.

The prosecutor’s office has also opened two criminal cases for alleged public calls for extremism and assistance to terrorism, Russian state media reports. The step follows Meta’s decision yesterday to temporarily change its hate speech policy to allow calls for violence against Russia in Ukrainian war posts.

Designating Meta as an extremist group would put it alongside the organization of Russia’s leading opposition figure Alexey Navalny, who is currently jailed. Membership or assistance to extremist organizations is punishable by lengthy prison terms, ranging from 5-10 years.

Russia’s state censor has already blocked access to Facebook. This raises the possibility that those using Facebook in the country could also face prison, though that is not clear.

-ABC News' Patrick Reevell

The U.N. said it is increasingly concerned about the nearly 2 million internally displaced people and nearly 13 million impacted by the Ukraine-Russia conflict.

Of particular concern are supplies of food, water, medicines and other necessities that are urgently needed in the hard-hit cities of Kharkiv and Mariupol, according to UNHCR spokesperson Matthew Saltmarsh. Access to these areas remains restricted because of military operations and hazards like land mines.

The U.N. High Commissioner for Refugees is working to provide heating stations at border crossings for those who are particularly vulnerable and is also working to roll out cash assistance.

-ABC News' Zoe Magee