A US air strike on Libya has killed more than 80 rebels from so-called Islamic State (IS), said outgoing US Defence Secretary Ash Carter. The mission, which dropped around 100 bombs on Wednesday, is thought to be the last signed by President Barack Obama as he prepares to leave office. Mr Carter said those targeted were "actively planning" attacks in Europe. President-elect Donald Trump takes over as the US's new commander-in-chief on Friday. On his last full day as defence secretary, Mr Carter said, "These were critically important strikes for our campaign and a clear example of our enduring commitment to destroy ISIL's [IS] cancer not only in Iraq and Syria but everywhere it emerges." The strikes hit military camps run by IS and located about 30 miles (45km) south-west of the coastal city of Sirte - an IS stronghold until the group was driven out in December. Two B-2 bombers flew a round-trip of around 34 hours from Missouri, US military officials said. It was the first time the stealth planes had been used in combat in Libya since March 2011, when they were deployed as part of the campaign to oust long-time leader Muammar Gaddafi. Libya has become increasingly divided since Gaddafi's fall, with competing governments and rival militias seeking to gain territory and influence.