August futures for North Sea Brent blend fell by 0.14%, to $61.98 per barrel, while August futures for WTI were 0.4% down, to $56.7 per barrel.
On Thursday, energy services firm Baker Hughes Inc published a weekly update on the number of drilling rigs in the United States, the total number of which increased by three units, or 0.34%, to 862 units. At this, the number of oil drilling rigs in U.S. fields rose by 12, bringing the total figure to 640 (1.91% up), Prime wrote with reference to Baker Hughes report.
In addition, investors' sentiments on Friday were influenced by a report that China's securities regulator said it had opened an investigation into suspected stock market manipulation after a slump of more than 20% in Chinese stocks since mid-June.
