Angelina Jolie meets wounded children and fans in western Ukraine

The war-torn city of Lviv, in western Ukraine, received an unexpected boost of star power on Saturday as Angelina Jolie paid a private visit to the region.

The actor, 46, is a special envoy for the United Nations High Commissioner for Refugees, but a spokesperson for the agency denied she was in the city, 80 kilometres from the Polish border, on official UN business.

"Angelina Jolie is travelling to Ukraine in her personal capacity and UNHCR has no involvement in this visit," UN spokesperson Matt Saltmarsh said in an email statement.

She was spotted in a café in the southeastern portion of the city on Saturday, where startled onlookers shot video that was subsequently posted on Twitter. At one point, she appeared to sign autographs and was accompanied by an unidentified man.

Later Jolie was also spotted at the city's central train station, where a video shows her shaking hands and speaking with people.

She reportedly visited children, now in the Lviv region, who had been injured earlier this month in a Russian airstrike on a train station at Kramatorsk in the eastern part of Ukraine.

Aside from the scattered social media posts, little else is known about the visit.

In early April, Jolie made a surprise visit to young Ukrainian war refugees being treated at the Bambino Gesù pediatric hospital in Rome.

She was quoted at the time in Italian newspaper Corriere della Sera as saying she was "praying for the end of the war" and that it was "the only way to stop the suffering and the fleeing from the areas of conflict."

Separately, in early March, Jolie visited Aden, Yemen, in her official UN capacity, a visit that helped draw attention to the catastrophic seven-year conflict and its effects on the people of that country.