KYIV, Ukraine—A series of cyberattacks on Tuesday knocked the websites of the Ukrainian army, the defense ministry and major banks offline, Ukrainian authorities said. Still, there was no indication the relatively low-level, distributed-denial-of-service attacks might be a smokescreen for more serious and damaging cyber mischief. At least 10 Ukrainian websites were unreachable due to the attacks, including the defense, foreign, and culture ministries and Ukraine’s two largest state banks. In such attacks, websites are barraged with a flood of junk data packets, rendering them unreachable. “We don’t have any information of other disruptive actions that (could) be hidden by this DDoS attack,” said Victor Zhora, a top Ukrainian cyberdefense official. He said emergency response teams were working to cut off the attackers and recover services. Customers at Ukraine’s largest state-owned bank, Privatbank, and the state-owned Sberbank reported problems with online payments and the banks’ apps. Among the attackers’ targets was …