MOSCOW—Russian President Vladimir Putin described Donald Trump as the “absolute front-runner” in the U.S. presidential campaign and a colorful and talented person, cheering the American real estate mogul’s calls to improve U.S.-Russian relations.

Mr. Putin made the comments Thursday after his annual news conference, during which he vowed to work with any leader U.S. voters elect. Afterward, the Russian president praised Mr. Trump, even as he cautioned it wasn’t Russia’s place to judge American candidates.

“He’s...