Associated Press The owner of the Wagner private military contractor made his most direct challenge to the Kremlin yet on Friday, calling for an armed rebellion aimed at ousting Russia’s defense minister. The security services reacted immediately by calling for the arrest of Yevgeny Prigozhin. In a sign of how seriously the Kremlin was taking the threat, security was heightened in Moscow and in Rostov-on-Don, which is home to the Russian military headquarters for the southern region and also oversees the fighting in Ukraine. While the outcome of the confrontation was still unclear, it appeared likely to further hinder Moscow’s war effort as Kyiv’s forces were probing Russian defenses in the initial stages of a counteroffensive. Prigozhin claimed early Saturday that his forces had crossed into Russia from Ukraine and had reached Rostov, saying they faced no resistance from young conscripts at checkpoints and that his forces “aren’t fighting against children.” “But we will destroy anyone who stands in our way,” he said in one of a series of angry video and audio recordings posted on social media beginning late Friday.