Russian president Vladimir Putin said he would only use force in Ukraine as a "last resort" as he defended Russia's actions in Crimea amid increased criticism from the US.

Speaking for the first time since the crisis escalated, Mr Putin said although force was not currently required, Russia reserved the right to defend its compatriots who were living in "terror" in Ukraine.

The Russian leader accused the West of promoting an "unconstitutional coup" in Ukraine, and claimed the forces which seized power in Crimea were "local forces of self-defence" not Russian soldiers.

ITV News' Diplomatic Correspondent John Ray reports:

Read: Would sanctions on Russia help to end the Ukraine crisis?

In other developments, tension remained in Crimea as Russian troops fired warning shots to stop protesting Ukrainian troops advancing further towards the Belbeck air base in the region.

Russia also successfully test-fired an Intercontinental Ballistic Missile, however the US said it had received proper notification of the country's plans.

Anti-war demonstrators outside Russia's defence ministry ended swiftly with dozens arrested according to reports.

Ukrainian Prime Minister Arseny Yatseniuk revealed that the Ukrainian and Russian governments had held talks on the crisis "at the level of ministers".

US President Barack Obama condemned Russian actions in Crimea claiming it had violated international law.

Mr Obama said Russia's legitimate interests in Ukraine did not give it a right to "use force as a means of exerting influence", and insisted the Ukrainian people should be able to decide their own future.

Putin has defended Russia's actions in Crimea despite criticism. Credit: ITV News

US Secretary of State John Kerry, visiting Kiev for the first time since the start of the uprising, warned that the US was prepared to take action to "isolate Russia".

Mr Kerry laid flowers in Independence Square at a memorial to protesters who were killed in violent clashes with police last month.

He also announced a $1 billion economic package and technical assistance to the new government.

U.S. President Barack Obama pauses as he answers a question about the situation in Ukraine. Credit: Reuters

Russia warned that it would retaliate against any sanctions imposed.

John Kerry will meet with Russian foreign minister Sergey Lavrov tomorrow to discuss the ongoing crisis.

Watch: New footage of tense stand-off between Russian and Ukrainian troops in Crimea