The Russian ruble plummeted almost 10% overnight, falling to its lowest level in more than four years, as oil prices crashed following the breakdown of the Russia-Saudi Arabia pact to limit production, The Moscow Times reports.

The ruble was trading at a low of 74.9 to $1 on Monday, March 9 morning, after another wild start to the week for financial markets. Russia’s rejection of a renewed round of oil production cuts in the OPEC+ format at a crunch meeting in Vienna on Friday shocked the global energy markets and has prompted analysts to talk of an “oil price war” between two of the world’s largest energy suppliers.

Benchmark Brent crude fell 30% to $33 a barrel when trading opened on Asian markets following the weekend, the sharpest one-day loss in almost three decades.

Falling oil prices put the Russian ruble under pressure, as Moscow still relies on energy exports for a large portion of its budget. The so-called budget breakeven rate is $50, while profits on oil sold about $42 a barrel are funnelled into Russia’s swelling National Welfare Fund (NWF).