Kenya has rejected Russia's recognition of Donetsk and Luhansk areas of Ukraine as independent states.
In a statement at the United Nations Security Council's urgent meeting on Ukraine, Amb Martin Kimani said Kenya was gravely concerned by the announcement by Russia.
"Kenya registers its strong concern and opposition to the recognition of Donetsk and Luhansk as independent states," he said.
"We further strongly condemn the trend - in the last few decades - of powerful states, including members of this Security Council, breaching International Law with little regard."
Kimani called on all UNSC member states to rally behind the council's Secretary general in defending multilateralism.
Kenya insisted that the territorial integrity and sovereignty of Ukraine had been breached, even as it urged use of diplomacy to solve the issues at hand.
Kenya is a member of the United Nations Security Council.
The remarks came shortly after Russian President Vladimir Putin ordered the deployment of troops to two breakaway regions in eastern Ukraine after recognising them as independent on Monday.
Putin's announcement drew international condemnation and immediate U.S. sanctions to halt U.S. business activity in the breakaway regions and ban import of all goods from those areas.
In a lengthy televised address packed with grievances against the West, a visibly angry Putin said eastern Ukraine was ancient Russian land.
Russian state television showed Putin, joined by Russia-backed separatist leaders, signing a decree recognising the independence of the two Ukrainian breakaway regions - the self-proclaimed Donetsk People's Republic and the Lugansk People's Republic.
Putin had announced his decision in phone calls to the leaders of Germany and France earlier, the Kremlin said.
In his address, Putin delved into history as far back as the Ottoman empire and as recent as the tensions over NATO's eastward expansion. His demands that Ukraine drop its long-term goal of joining the Atlantic military alliance have been repeatedly rebuffed by Kyiv and NATO states.
"I deem it necessary to make a decision that should have been made a long time ago - to immediately recognise the independence and sovereignty of the Donetsk People's Republic and the Lugansk People's Republic," Putin said.
