Ben Stiller meets Volodymyr Zelenskyy in Ukraine on World Refugee Day

Hollywood actor and director Ben Stiller heaped praise on Ukrainian President Volodymyr Zelenskyy in Kyiv on Monday to mark World Refugee Day as Russia's ongoing invasion there forces millions to flee.

Stiller, who was visiting Ukraine and Poland as a goodwill ambassador of the United Nations High Commissioner for Refugees (UNHCR) gave a rushed walk and extended his hands to meet Zelenskyy, an actor and stand-up comedian before he was elected president in 2019.

Both men said they were honored to meet each other.

"You're my hero," Stiller told Zelenskyy inside the presidential palace. "You're amazing. You quit a great acting career for this."

"Not so great as yours," Zelenskyy said back with a smile.

"No, but pretty great," Stiller joked, putting his hand over his heart at times. "But what you've done and the way that you've rallied the country and for the world, it's really inspiring."

Zelenskyy gushed at the compliment, saying, "It's too much for me."

Stiller traveled to Ukraine "to see the scale of destruction and hear firsthand from people who have directly experienced the impact of the war," the UNHCR said in a release, adding, "These personal stories will enable Mr. Stiller to communicate the need for continued and increased support to the humanitarian response in Ukraine."

Ahead of his meeting with Zelenskyy and Ukrainian Foreign Minister Dmytro Kuleba, Stiller visited occupied settlements around Kyiv and stopped earlier Monday in Irpin -- a town next to the capital that witnessed intense fighting early during the invasion. He and Karolina Lindholm Billing, the UNHCR representative in Ukraine, met with survivors of that occupation, according to a press release from Zelenskyy's office.

"It's one thing to see this destruction on TV or on social networks. Another thing is to see it all with your own eyes. That's a lot more shocking," Stiller told Zelenskyy.

"What you saw in Irpin is definitely dreadful," the Ukrainian president replied. "But it is even worse to just imagine what is happening in the settlements that are still under temporary occupation in the east."

In Irpin, the bodies of 290 victims, with a disproportionate number of women, were recovered after Russian forces inflicted a month of terror, the BBC reported.

And in the east, Russian forces have used long-range artillery to assail cities in the Donbas region, which Russian President Vladimir Putin seeks to control.

Since Putin launched his invasion in late February, between 8 and 12 million people have fled their homes in Ukraine, according to data from the UNHCR. Roughly half have fled to neighboring Poland, which Stiller visited Sunday, seeking to spread awareness of the needs of the refugee crisis.

ABC News' Christine Theodorou contributed to this report.