Pope Francis has come under criticism for telling Russian youths last week to remember that they are the heirs of past tsars such as Peter the Great, whom President Vladimir Putin has held up as an example to justify Moscow's actions in Ukraine.

The Ukrainian government said the comments, which Francis made in a live video address to Catholic youths gathered in St. Petersburg, were "deeply regrettable".

While the Vatican issued a statement on Tuesday saying the Pope had no intention of glorifying past Russian imperialism, Kremlin spokesman Dmitry Peskov praised the Pope during a briefing on the same day.

"The pontiff knows Russian history and this is very good," he said. "It has deep roots, and our heritage is not limited to Peter (the Great) or Catherine, it is much more ancient."

Russians traditionally trace the origins of their nation to a group of medieval principalities centered around Kyiv known as Kievan or Kyivan Rus. Putin has sought to deny that Ukraine has any tradition of statehood and said that Russians and Ukrainians are one people, in what Ukrainian and western scholars have called a false and self-serving view of history.

"What the (Russian) state, activist groups, school and university teachers are doing now is carrying this heritage to our youth, reminding them of it," Peskov said.

"And the fact that the pontiff sounds in unison with these efforts is very, very gratifying."

(Reporting by Reuters; editing by Mark Trevelyan)