There would be "havoc" if Greece left the euro zone and adopted an alternative currency, Willem Buiter, global chief economist at Citi, told CNBC.
Finland has informed its 900,000 military reservists of their roles in the event of a military crisis against a backdrop of rising tensions.
European Central Bank chief Mario Draghi said the economic outlook for the euro zone looks "brighter today than it has done for seven long years."
The euro zone economy continued to lose momentum in May, PMIs showed, but it's not all bad news, with hiring in the region on the up.
There is a "high likelihood" of capital controls being introduced in Greece, according to a report published by Moody's on Wednesday.
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