The U.S. President has warned Russia that its 'incursion' into Ukraine will have consequences.

Russia is denying claims by NATO that over 1,000 Russian troops are fighting with pro-Russian separatists.

The presence of Russian troops in Ukraine was discussed at the United Nations last night, and NATO is holding an emergency meeting today to discuss the escalating crisis.

America's accused Moscow of lying outright over its actions.

The United States Ambassador to the UN is Samantha Power: