Sri Lanka, Dec. 4 -- NATO foreign ministers on Tuesday called on Russia to de-escalate the situation via Ukraine, warning they stand in solidarity with Ukraine.

Speaking from Riga, Latvia, where NATO foreign ministers gathered for a summit, Secretary-General Jens Stoltenberg said the build-up of Russian troops and military equipment near the Ukrainian border "is unprovoked and unexplained."

"We see Russian military build-up, we see heavy armour, we see drones, and combat-ready troops.Russia needs to be transparent, and they need to reduce tensions, and de-escalate," he added.

He stressed that although Ukraine is not a NATO ally - and therefore does not fall under Article 5 for Collective Defense - it is "a highly valued partner".

"We ...