"Geopolitical risks are clearly back on the crude oil agenda after having been absent nearly entirely since the oil market ran into a surplus in the second half of 2014", Bjarne Schieldrop, chief commodities analyst at SEB, said, also citing Kurdistan and Libya.
The spread between US crude and Brent hit the narrowest in almost two weeks.
Oil prices were up slightly on Thursday as a pipeline outage in Britain continued to lift Brent crude prices.
Ongoing protests in Iran have led to a hardening of crude prices to levels last seen in mid-2015.
"Iran is one of the biggest Middle Eastern members of Opec [Organisation of the Petroleum Exporting Countries] and the current turmoil in the country could potentially have a much larger impact on the oil price", said Naeem Aslam, the chief market analyst at Think Markets.
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The 14-member cartel, Russian Federation and nine other crude producers announced plans to extend their output cuts until the end of 2018.
Extreme cold weather across much of North America could also boost US crude prices by causing production problems in the oilfields.
Brent rose 0.6% to $67.29 a barrel on the London-based ICE Futures Europe exchange at 7.16am local time.
Even without the unrest in Iran, which is a major oil exporter, market sentiment was bullish.
However, rising US production, which is on the verge of breaking through 10 million bpd, has tempered the bullish outlook. In the last quarter of 2016, Russia's production had hit a post-Soviet era high, while year over year in 2016, production grew to 10.96 million bpd, from 10.72 million bpd in 2015.
For the whole of 2017, Russia's average annual oil production increased for a ninth year in a row.