The UK and US governments have warned Russia not to use humanitarian assistance as a pretext for sending troops into eastern Ukraine.
US Ambassador to the UN, Samantha Power, says any such intervention would be completely unacceptable and viewed as an invasion of Ukraine.
The UK Foreign Secretary, Philip Hammond, has urged Russia to “avoid any provocative actions”.
His office cited reports that Russian military vehicles had entered Ukraine.
Heavy fighting continued today in eastern Ukraine, near the Russian border, between Ukrainian government forces and pro-Russia militants.