"Here you are also confronted with a situation that represents another part of the Russian military doctrine: the idea of hybrid warfare," she told German troops stationed in Lithuania as part of a NATO force deployed to deter Russia.

NATO allies have accused Russia of using "hybrid warfare" techniques, including subversion, propaganda and cyber warfare, to undermine the West without triggering a full NATO military response.

Russia has repeatedly denied that it stages such attacks and has accused the US-led alliance of provoking an arms race.

"Hybrid warfare is not something that we are very used to. You clearly experience this here in very specific ways," Merkel added, without elaborating.

"It is not for nothing that we built in Germany a special cyber unit within the German military in order to build capabilities in this area," she told troops at their base in Rukla, northwest of the capital Vilnius.

Last year, Germany deployed over 500 troops in Lithuania as part of a NATO mission to reassure eastern allies and deter Russia.

Soon after their arrival, German troops were subjected to false rape accusations while media reports said Moscow also targeted NATO soldiers' smartphones.

Fears that Russia could attempt to attack NATO's ex-communist states surged after Moscow's 2014 annexation of Crimea from Ukraine, a move that sent East-West relations to their lowest point since the Cold War.

Besides Lithuania, 1,000-strong NATO battalions were also deployed in fellow Baltic states Latvia and Estonia and neighbouring Poland.