Crude oil just crashed below $40 per barrel for the first time since 2009.

West Texas Intermediate crude oil futures in New York fell more than 3% to as low as $39.89 per barrel.

On Friday afternoon, data from driller Baker Hughes showed that the oil rig count climbed by two to 672 — the fifth straight week with a rise. Shortly after the data release, WTI slipped below $40.

The slide toward $40 per barrel gained momentum earlier this week after the US Energy Information Administration reported a larger-than-expected build in crude inventories last week.

This added to signs that the oil market remains oversupplied, with unequal demand, as the 12-member oil cartel OPEC continues to pump at an unrelenting pace. The group's latest monthly report showed that its output surged to a three-year high in July, boosted by Saudi Arabia, Iraq, Angola, and Iran. More Iranian oil is expected on the market when economic sanctions are lifted.

Oil is now headed for its longest weekly losing streak since 1986, according to Bloomberg. Oil is in a bear market, and prices are down nearly 35% from recent highs.

Friday's drop comes amid a bigger sell-off in global markets. The major averages are seeing their sharpest weekly loss of the year, and the Dow lost more than 350 points during Friday's session.

Brent crude oil, the international benchmark, fell to $45.10, the lowest level in six years.

Here's a chart showing the slide in WTI Friday:

And during the past few years: