Canada has ordered the children and family members of its embassy staff in Ukraine to leave the country as the possibility of a Russian invasion looms. 

The decision comes after Britain said it would pull some of its diplomats out of its Ukraine embassy, and after the U.S. State Department decided to order the families of its Ukraine embassy personnel to leave.

Russia has positioned about 100,000 troops across Ukraine's borders along with tanks and other heavy artillery, stoking fears across Europe of an invasion, something Russia has denied.

Tensions escalated on Monday as the U.S. placed 8,500 troops on heightened alert in Europe. 

NATO also announced a series of what it called "enhanced deterrence and defence" deployments of ships, fighter jets and troops in an attempt to show heightened solidarity.

On Tuesday, Ukraine's leaders tried to project calm, saying that a Russian invasion was not imminent, but Global Affairs Canada said the time had come for the country to downsize the Canadian diplomatic footprint in Kyiv. 

"The safety and security of Canadians, our personnel and their families at our missions abroad is our top priority. Due to the ongoing Russian military buildup and destabilizing activities in and around Ukraine, we have decided to temporarily withdraw Canadian embassy staff’s children under 18 years of age and family members accompanying them," Global Affairs said in a statement.

"Officials at Global Affairs Canada and at the Embassy of Canada to Ukraine in Kyiv will continue to closely monitor the situation."