Nato is planning to fly the E-3 airborne warning and control system (AWACS) aircraft over Poland and Romania in a bid to monitor the escalating crisis in neighbouring Ukraine.

An unnamed Nato spokesman was quoted by Reuters as saying that all AWACS reconnaissance flights will take place solely over the alliance's territory in the coming days.

"This decision is an appropriate and responsible action in line with Nato's decision to intensify our ongoing assessment of the implications of this crisis for Alliance security," the spokesman said.

All AWACS missions are scheduled to be flown from their respective home bases in Geilenkirchen, Germany, and from the Royal Air Force (RAF) Waddington base in Lincolnshire, UK.

The AWACS flights recommendation came from the Nato Allied Command Operations Supreme Allied Commander Europe US Air Force general Philip Breedlove yesterday, and was shortly approved by the ambassadors of 28 Nato member states in Brussels, Belgium.

"The deployment comes as Russia strengthens its presence in Crimea."

The deployment comes as Russia strengthens its presence in Crimea, an autonomous Ukrainian region with a majority ethnic Russian population, which is currently preparing for referendum on whether to split off and become a part of Russia.

Russia news agency, Interfax quoted unnamed sources in the Crimean legislature as saying: "An invitation has been handed to Switzerland, the country that holds the rotating presidency of the OSCE, for representatives of the member countries and of the Office for Democratic Institutions and Human Rights to monitor voting at the March 16 referendum in the Crimea."

Both houses of the Russian Parliament have announced support for Crimea if it votes to leave Ukraine and join Russia, Press TV reports.