BRUSSELS (Reuters) - Canada's Prime Minister Justin Trudeau said on Tuesday his country was sending 150 additional troops to Latvia and extending its military operations in eastern Europe, known as Operation Reassurance, following Russia's invasion of Ukraine.

       The Canadian forces were first sent to Europe in response to Russia's 2014 annexation of Crimea and extended to Latvia in 2016. He did not go into details.

       During the visit to Latvia with Trudeau, NATO Secretary-General Jens Stoltenberg said that Russia's President Vladimir Putin had "seriously underestimated" Ukraine as well as that of NATO's resolve.

       Spain's Prime Minister Pedro Sanchez, also in Latvia, said Putin was "alone" and that the world was with Ukraine.

       (Reporting by Robin Emmott and Sabine Siebold)