Russia's recession worsened in the second quarter as gross domestic product shrank by 4.6 percent compared with a year earlier, battered by lower oil prices and Western sanctions over Ukraine, official statistics said Monday.

The preliminary estimate from the official Rosstat agency marks a steep drop from the 2.2 percent contraction in the first quarter of 2015, and is worse than an earlier government forecast of 4.4 percent.  

A sharp contraction had been widely expected, with Russian officials saying that the country's economic crisis has reached its nadir.

But a new fall in crude oil prices has sparked a fresh drop in the ruble in recent months and thrown assertions that the country has shuffled off the worst of the crisis into doubt.

The drop in GDP is Russia's sharpest contraction since 2009, according to Bloomberg.

"We hope that 2Q of this year could mark the bottom of the current cycle, and 2015 numbers could look somewhat better," Oleg Kouzmin, an economist at Renaissance Capital, said in a note.

"We expect GDP growth to fall by 3.6% in a whole of 2015, but that requires $60 per barrel of oil, so the fall could be closer to 4% if oil stays at current levels."