Russia's ambassador to the UK was summoned after two Russian bombers disrupted civilian air traffic over the English Channel.
Russian Finance Minister Anton Siluanov told CNBC that Russia would consider giving financial help to debt-ridden Greece.
China and the U.S. dominate London's property, as the city's lucrative property price rises and rental incomes continue to appeal to foreign buyers.
The Danish central bank cut its key policy rate for the third time in two weeks following intervention on the foreign currency market.
Get the best of CNBC in your inbox
Jürgen Matthes, international director at Cologne Institute for Economic Research, says that if Greece accepts Russian financial aid it will create a "major diplomatic irritation".
Andrey Kostin, CEO of VTB, says the Russian central bank needs to cut interest rates.
Russian finance minister Anton Siluanov says he hopes the country's central bank will lower interest rates at its meeting today.