At least four people were killed in Crimea on Thursday following Ukrainian attacks on Simferopol and a commuter train, according to Moscow-installed authorities. These strikes occurred a day after Ukraine targeted energy and military sites in Saint Petersburg, coinciding with Russia's major economic forum. Ukraine has described these actions as justified retaliation for continuous Russian assaults on its territory, while US Secretary of State Marco Rubio expressed concern about the escalating risk of the conflict. Kremlin spokesman Dmitry Peskov vowed a "systemic" Russian response to the Saint Petersburg attacks, which generated visible black smoke near the forum venue. Ukrainian officials stated their strikes aimed to disrupt the economic conference.