A conference organized by Ukrainian lawmaker Yulia Tymoshenko's Batkivshchyna (Fatherland) party was briefly interrupted by a protester who stripped to the waist to reveal a slogan and an arrow pointing to his behind.
Tymoshenko, a former prime minister and opposition leader, was on the podium preparing to address the party's New Course For Ukraine forum when a young man approached her and offered her flowers.
The man then briefly took off his T-shirt, revealing the message "The new course of Ukraine" written on his back and a thick red arrow pointing to his bottom.
Tymoshenko reacted to the incident with humor, smiling and telling the audience, "It was impromptu, but it will make our forum livelier."
She then offered her views about how to implement political and judicial reforms in Ukraine to tackle "widespread and deep-rooted corruption," and raised the idea of switching from a presidential system of government to a parliamentary system in which the prime minister has more power.
Tymoshenko, who served as prime minister in 2005 and 2007-10, has said that Batkivshchyna intends to run in 2019 parliamentary elections and field a candidate in the presidential election the same year.
There has been speculation that Tymoshenko plans to run for president, but she made no announcement on that issue at the forum. She said that her party will hold similar gatherings in the future to share ideas on economic reforms and other matters.
The conference was streamed live on Facebook.