Ukraine security service sources tell BBC bombers "are burning en masse" - as Russia confirms Kyiv's drone attack.

Ukraine has carried out large-scale drone strikes against four airbases deep inside Russia, destroying multiple combat planes, according to a source in the Ukrainian Security Service (SBU).

A truck pulled in, and drones flew out of it.” From an airbase near Murmansk, in Russia’s far north, came similar stories: “The driver’s running around...drones are flying from his truck toward the base.

With 41 military aircraft impacted, the Ukrainian drone attack was described by some commentators as Russia's "Pearl Harbor." The attack on Pearl Harbor in December 1941 was a surprise air raid by Japan on the U.S. during World War II. Kyiv's assault follows ground advances by Moscow troops in recent days in Ukraine's Sumy border region.

Russian Foreign Minister Sergei Lavrov and U.S. Secretary of State Marco Rubio discussed on Sunday prospects for settling the conflict in Ukraine and Russia-Ukraine talks set for Monday in Turkey, Lavrov's ministry said.

By making harsh, uncompromising demands in peace talks with Ukraine while continuing to pummel it with waves of missiles and drones, Russian President Vladimir Putin is sending a clear message: He will only accept a settlement on his terms and will keep fighting until they’re met.