International crude benchmark Brent traded at $81.70 per barrel at 1316GMT on Friday, while American benchmark West Texas Intermediate (WTI) saw $72.09.
Brent crude reached its highest level on Monday since November 2014, rising 2.5 percent to $80.78, after closing at $78.80 the previous week.
The rise in oil prices was driven by the decision of OPEC members and Russia to hold production levels unchanged which increased worries about potential supply issues in the global market amid approaching U.S. sanctions on Iran and declining output in Venezuela.
On Wednesday, Iran’s Petroleum Minister Bijan Namdar Zangeneh blamed oil price volatility on Washington’s 'anti-Iran policies'.
'It's impossible to keep oil prices down while simultaneously reducing Iran’s oil exports,' Zangeneh said.
However, experts contend that expected increase of Saudi Arabia's oil production could offset the drop in Iranian production.
A new round of U.S. sanctions on Iran, the third-largest producer in OPEC, kick in on Nov. 4.
US$1 equals 6 Turkish liras.
By Firdevs Yuksel and Zeynep Duyar
Anadolu Agency
energy@aa.com.tr