In the latest development of the crisis between Russia and Ukraine, Russia's defence ministry has announced its decision to hold military exercises this week near the Ukrainian border.
Around 100 aircraft, including fighter jets, bombers and helicopters are expected to take part in the operation in the west of the country, a spokesman for the Russian government said.
Ukraine, however, was not mentioned by the Russian spokesman, who told the Interfax news agency that the exercise was just the first in a series intended to improve the response of the Russian air force.
Russia's decision is likely to attract strong criticism from western governments, who along with Ukraine have previously accused Russia of boosting its troops and armoury in the parts of the country closer to the border with Ukraine.
Ukraine, meanwhile, has announced that it was making significant gains against rebels in the eastern parts of the country, where civilians are now preparing for a siege as government forces look set to close in on Luhansk and Donetsk.
Both cities are currently in the hands of the pro-Russian rebels, who have declared independence from Kiev and whose ranks and arsenal have been boosted by Russia, which angered Ukraine and other western governments.
In response to Moscow's support for pro-Russian rebels, last week the European Union imposed sanctions on Russia, designed to target the country's defence, banking and energy sectors and on Sunday the German Vice Chancellor, Sigmar Gabriel, insisted that new tough economic sanctions against Russia were necessary, even though they will hurt Germany's economy.
"What would happen if the European Union didn't react?" said Gabriel in an interview on Germany's ZDF channel.
"If all the lessons learned in Europe are that someone can start a civil war in a neighbouring country and nothing happens, then that would cost a lot more than a few percentage points of possible growth," continued Gabriel.
"There would be much, much greater negative consequences if Europe did not act ... Where war and peace are at stake, economic policies can't be the main concern."
Germany is the EU's largest economy and has conducted extensive business with Russia but that didn't prevent Chancellor Angela Merkel from becoming a strong advocate of tougher sanctions against Moscow, after pro-Russian rebels shot down flight MH 17 over eastern Ukraine last month.
On Friday, however, Russian president Vladimir Putin described the sanctions as "counterproductive".
"The Russian leader described Washington's course of ramping up sanctions pressure as counterproductive, causing serious damage to bilateral relations and international stability in general," the Kremlin said in a statement.