Geronimo! Reuters/Yuri Maltsev After a few strong weeks, the ruble fell again following a new offensive in Ukraine and another drop in oil prices.

On Wednesday, the ruble slipped nearly 2.7% to a 6-week low of 54.26 rubles.

The currency's plunge follows reports of fighting with "heavy artillery and tanks" in the Donetsk-region towns of Maryinka and Krasnohorivka after a relatively quiet three-month period.

"Any sign of an escalation of the conflict in Ukraine is going to cause concern in the Russian markets," William Jackson, an analyst at Capital Economics Ltd. told Bloomberg. "It increased the likelihood that sanctions may be renewed or extended."

Furthermore, oil prices fell on Wednesday. Brent crude dropped 2% (getting as low as 2.7% during the day), while WTI fell 1.8%.

Ruble versus USD, one day Bloomberg

The ruble's been the best-performing currency this year following the rebound in oil prices and the relatively quiet ceasefire in Ukraine.

It even got so strong at one point in May, the Central Bank announced that it would start buying $100-$200 million per day to replenish reserves.

But if the conflict in Ukraine heats up, and/or oil prices plunge again, the ruble may fall again.