Russian invasion in Ukraine must be considered by the UN Security Council as act of aggression, UN must react accordingly, this is war"— Edgars Rinkēvičs (@edgarsrinkevics) August 28, 2014
Rinkēvičs was tweeting from Milan, Italy where he is attending an informal meeting of the European Union's General Affairs council.
Later in the day a statement released by the Foreign Ministry said: "Latvia condemns the invasion of Ukraine carried out by the armed forces of the Russian Federation. This is open aggression against Ukraine's state sovereignty and territorial integrity and undermines the basic principles of international law."
"Latvia calls on Russia to immediately withdraw its troops from the territory of Ukraine," the statement said.
Later in the day Prime Minister Laimdota Straujuma added her voice to the condemnation of Russia's actions, tweeting:
"I condemn the [Russian Federation] armed invasion of Ukraine, Latvia will invite international organizations to decide on measures to counter Russian aggression."
Nosodu KF bruņoto spēku invāziju Ukrainā, Latvija aicinās starptautiskās organizācijas lemt par pasākumiem Krievijas agresijas apturēšanai.— Laimdota Straujuma (@Straujuma) August 28, 2014
In a media statement Latvian Defense Minister Raimonds Vejonis said: "In the last hours, the Russian Federation has shown its true colors in carrying out the invasion of Ukraine."
Russia had spurned chances to solve disputes peacefully and instead chosen "to exercise their geopolitical ambitions in a violent way," Vejonis said.
The direct military threat to Latvia remained "low", Vejonis said, while welcoming the start of training exercises involving several hundred NATO troops on Latvian soil next week.
The Latvian stance was closely echoed by Lithuanian Foreign Minister Linas Linkevicius who tweeted:
The diplomats' call for UN action came as evidence mounted that regular Russian troops had crossed the Ukrainian border and engaged Ukrainian forces.
Also Thursday the European Union issued a statement via the Organization for Security and Cooperation in Europe in Vienna saying: "We are deeply concerned by the recent reports of Russian soldiers and military vehicles on Ukrainian territory; of continuing and intensified crossborder shelling; and of violations of Ukrainian airspace by the Russian Federation."