Bono and The Edge performed at a Kyiv bomb shelter on Sunday after being invited by Ukrainian leader Volodymyr Zelenskyy.
During their surprise 40-minute gig, the U2 rockers showed their support for Ukrainians fending off the current Russian invasion with the Ben E. King song Stand by Me at Khreschatyk metro station, which is serving as a bomb shelter.
They were joined by another singer in Ukrainian military fatigues, Billboard reports.
Posting on U2's Twitter account, Bono and The Edge told their followers: "President @ZelenskyyUa invited us to perform in Kyiv as a show of solidarity with the Ukrainian people and so that's what we've come to do. -- Bono and The Edge #StandWithUkraine."
During their set, the 61-year-old frontman rallied the crowd with messages of support, telling the audience, "You're fighting for all of us who love freedom."
Bono also visited Bucha, a town outside Kyiv where hundreds of bodies were found after Russian troops withdrew last month.