By Jeff Mason

(Reuters) -- First Lady Jill Biden made an unannounced trip to Ukraine on Sunday to show support for its people amid Russia's invasion, visiting a school that is serving as a temporary shelter and meeting Ukraine's first lady, Olena Zelenska.

"I thought it was important to show the Ukrainian people that this war has to stop and this war has been brutal and that the people of the United States stand with the people of Ukraine," Biden said, according to a report by a Washington Post reporter shared with other media organizations.

The school is serving as a shelter for 163 displaced Ukrainians, including 47 children, the report said.

Biden, who had been traveling in neighboring Slovakia, gave flowers to Zelenska, who was making her first public appearance since the Russian invasion began on February 24, according to a U.S. official. The two women hugged.

Zelenska said Biden was courageous for making the trip.

"We understand what it takes for the U.S. first lady to come here during a war when the military actions are taking place every day, where the air sirens are happening every day even today," she said through an interpreter, according to the report.

"We all feel your support and we all feel the leadership of the U.S. president, but we would like to note that the Mother's Day is a very symbolic day for us because we also feel your love and support during such an important day."

President Joe Biden has been leading efforts to impose economic sanctions on Russia and pressure President Vladimir Putin to end the war. The U.S. president has not been to Ukraine since the invasion, but other top U.S. officials have: Secretary of State Antony Blinken, Defense Secretary Lloyd Austin, and House Speaker Nancy Pelosi visited Kiev in the last two weeks.

Jill Biden returned to Slovakia after her trip across the border.

(Reporting by Jeff Mason; editing by Lisa Shumaker and Daniel Wallis)