Nato member countries have approved a new interim quick-reaction military force to protect themselves from Russia or other threats, the alliance's chief said.

The initial unit, to be up and running in early 2015, is designed to be supplanted the following year by a permanent force, Nato secretary-general Jens Stoltenberg said.

The foreign ministers of the 28 Nato member countries also approved maintaining measures through 2015 initiated to reassure Nato countries nearest Russia, Mr Stoltenberg said.

Such measures include stepped-up air patrols over the Baltic Sea and rotating Nato military units in and out of countries like Poland and the Baltic republics.

"We are protecting our allies and supporting our partners," Mr Stoltenberg told reporters.

The ministers' one-day meeting in Brussels was Nato's most important gathering since a September summit in Wales.

Later today, the ministers were expected to authorise the launch of an advisory mission in Afghanistan on January 1, when Nato-led combat operations there are scheduled to end.

The foreign ministers also condemned what they called Russia's "continued and deliberate destabilisation" in Ukraine, and announced new non-lethal assistance for Ukraine's military.

After speaking with Ukrainian counterpart Pavlo Klimkin by video link, they criticised Russia's reported military build-up in Crimea and Kremlin plans for a military expansion in the Black Sea region.

The ministers said in a joint statement that Russia's actions "undermine the security of Ukraine and have serious implications for the stability and security of the entire Euro-Atlantic area".

To help finance the reform and modernisation of Ukraine's military, Nato had announced the creation of so-called trust funds.

The ministers said the funds are now operational for logistics, cyber defence, rehabilitation of wounded soldiers and other uses.

"The choice of Ukraine to join the family of European democracies is clear and it has to be respected," Mr Stoltenberg said.