Oil prices have dropped below $100 per barrel for the first time in more than a week after a massive earthquake spawned a tsunami that slammed into northern Japan.

Japan is the third-largest oil importer in the world. It's unclear how much its economy will be affected by the disaster. But the news helped slow down what had been a three-week rally in oil markets.

Benchmark West Texas Intermediate for April delivery tumbled $2.80, or 2.7 percent, to $99.90 per barrel on the New York Mercantile Exchange. The price crossed the $100 mark last week because of Middle East tension. It was around $86 just three weeks ago.