US first lady Jill Biden has made an unannounced visit to western Ukraine, holding a surprise meeting with her Ukrainian counterpart Olena Zelensky as Russia presses its punishing war in eastern regions.

Mrs Biden travelled under the cloak of secrecy, becoming the latest high-profile American to enter Ukraine during its 10-week-old conflict with Russia.

She told Mrs Zelensky: “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.”

The first lady travelled by vehicle to the town of Uzhhorod, about a 10-minute drive from a Slovakian village that borders Ukraine.

The two came together in a small classroom, talking in front of reporters before they met in private. Mrs Zelensky and her children have been at an undisclosed location for their safety.

The Ukrainian president’s wife thanked Mrs Biden for her “courageous act” and said: “We understand what it takes for the US first lady to come here during a war when military actions are taking place every day, where the air sirens are happening every day – even today.”

The school has been turned into transitional housing for Ukrainian migrants from elsewhere in the country.

The visit allowed Mrs Biden to conduct the kind of personal diplomacy that her husband would like to be doing himself.

President Joe Biden said during his visit to Poland in March that he was disappointed he could not visit Ukraine to see conditions “first hand” but that he was not allowed, probably due to security reasons.

The White House said as recently as last week that the president “would love to visit” but there were no plans for him to do so.

The meeting came about after the two first ladies exchanged correspondence in recent weeks, according to US officials.

Mrs Biden’s visit follows recent stops in the war-torn country by US House speaker Nancy Pelosi and other members of Congress, as well as a joint trip by US secretary of state Antony Blinken and defence secretary Lloyd Austin to meet President Volodymyr Zelensky in Kyiv.

Canadian Prime Minister Justin Trudeau also made a surprise visit to Ukraine on Sunday, heading to Irpin, which was damaged by Russia’s attempt to take Kyiv at the start of the war, according to Ukrainian media outlet Suspilne and Irpin’s mayor Olexander Markushyn.

Earlier, in the Slovakian border village of Vysne Nemecke, she toured its border processing facility, surveying operations set up by the United Nations and other relief organisations to assist Ukrainians seeking refuge.

Mrs Biden attended a religious service in a tent set up as a chapel, where a priest intoned: “We pray for the people of Ukraine.”

Before that, in Kosice, she met and offered support to Ukrainian mothers in Slovakia who have been displaced by Russia’s war and assured them the “hearts of the American people” are behind them.

At a bus station in the city which is now a 24-hour refugee processing centre, Mrs Biden had an extended conversation with a Ukrainian woman who said she struggles to explain the war to her three children because she cannot understand it herself.

“I cannot explain because I don’t know myself and I’m a teacher,” Victorie Kutocha said.

“It’s so hard to understand,” the first lady replied.

The 24-hour facility is one of six refugee centres in Slovakia, providing an average of 300 to 350 people daily with food, showers, clothing, emergency on-site accommodation and other services, according to the White House.

Mrs Biden also dropped in at a Slovakian school that has taken in displaced students.

In recent weeks border crossings have averaged fewer than 2,000 per day, down from more than 10,000 per day immediately after Russia’s invasion on February 24.

Mrs Biden is on a four-day visit to eastern Europe to highlight US support for Ukrainian refugees and for the allied countries such as Romania and Slovakia that are providing a safe haven for them.

She spent Friday and Saturday in Romania, visiting US troops and meeting Ukrainian refugee mothers and children.