Brent crude oil hit $100 a barrel and stock futures fell sharply late Wednesday after blasts were heard in Ukraine and Russian President Vladimir Putin announced a military operation in Donbas.

Dow futures lost nearly 700 points, or about 2%. Nasdaq futures dropped 2.7%.

Brent crude, the world benchmark, briefly climbed above $100 a barrel for the first time since 2014. US crude jumped 3.3% to $95.15 a barrel.

The market turbulence comes as CNN teams in Ukraine reported explosions.

Oil supplies are already very tight. Analysts have warned that any disruptions to oil flows from Russia, the world's No. 2 oil producer, would drive prices even higher. (CNN)