Stoltenberg was speaking in Georgia during his South Caucasus trip.
ADVERTISEMENTNATO's Secretary-General Jens Stoltenberg said Monday that presidential elections in Russia were "neither free nor fair".
Speaking at a news conference in Tbilisi, Georgia, Stoltenberg added that Russia's organisation of elections "in occupied parts of Georgia and Ukraine" was "completely illegal".
"Georgia is facing complex security challenges. Russia persists in its pursuit of its imperial ambitions, and in Ukraine, the situation on the battlefield remains difficult. So, it is vital that we continue to step up our support," he added.
Stoltenberg, who was in Georgia's capital as part of his South Caucasus trip, met with the country's Prime Minister Irakli Kobakhidze. They discussed Black Sea security problems and the strengthening of Georgia's NATO cooperation.
Kobakhidze thanked the NATO Secretary-General for supporting Georgia's sovereignty and territorial integrity.
Stoltenberg arrived in Tbilisi from Baku where he discussed cooperation between Azerbaijan and NATO with officials from Azerbaijan's Defense and Foreign ministries.
On Sunday Stoltenberg met with the President of Azerbaijan Ilham Aliyev.
His tour concludes on Tuesday in Armenia.