Polish Foreign Minister Radoslaw Sikorski accused Russia of "an act of state terrorism" on 20 Nov. and promised a response "more than just diplomatic" after an explosion damaged rail tracks used to deliver aid to Ukraine, with authorities identifying two Ukrainian citizens who allegedly carried out the attack on Russian orders.
Because Russia (and, well, lots of other countries, including China and the US) commonly runs, amongst other things, foreign intelligence and influence operations out of consulates and embassies on a covert basis. Officially closing embassies/consulates tends to make it harder for hostile states that own those properties to execute hostile actions within the host country.
I was referring to the deployment of troops.
FTA:
Why don’t you just sign up to fight for Russia, you love it so much?
Oh, you poor thing.