PM Antonis Samaras's decision to call an early vote in parliament to elect a new president has caused fresh concerns.

Crude prices have plunged roughly 50 percent since June, weighed down by plentiful supplies, the stronger dollar and weak demand.

Dzhokhar Tsarnaev faces the death penalty if convicted of the largest mass-casualty attack on U.S. soil since September 11, 2001.

GM has come under fire from U.S. regulators and politicians for its failure to identify the problem earlier and alert consumers.

"This decision is aimed at limiting substantially increased ruble depreciation risks and inflation risks," the central bank said.

"Make no mistake. Our coalition isn't just going to degrade this barbaric terrorist organization. We're going to destroy it," Obama said.

Wassily Kandinsky only began his artistic career at the age of 30, having previously studied law and economics at university.

Local media have named those who died as cafe manager Tori Johnson, 34 and Sydney lawyer Katrina Dawson, 38.