A senior Russian general had advance knowledge of Yevgeny Prigozhin’s plans to rebel against Russia’s military leadership, according to U.S. officials briefed on American intelligence on the matter, which has prompted questions about what support the mercenary leader had inside the top ranks.

The officials said they are trying to learn if Gen. Sergei Surovikin, the former top Russian commander in Ukraine, helped plan Mr. Prigozhin’s actions.