US crude settled at $136.74 a barrel, up $1.38. London Brent crude was up $0.99 at $136.24 a barrel.
Nigeria’s senior oil workers union began a limited strike at Chevron on Monday. While the stoppage has not disrupted production yet, it added to concerns about supplies from the OPEC nation after militant attacks shut 340,000 barrels of daily production last week.
European Union approved new sanctions on Iran, including an asset freeze on its biggest bank, over its refusal to meet demand to end its nuclear program.
Concern over tensions between Iran and the West over Tehran’s nuclear programme have supported prices over the past year.
Israel carried out a large military exercise earlier this month which appeared to be a rehearsal for a potential bombing of Iran’s nuclear facilities, according to a New York Times story.
Energy experts are concerned any conflict in Iran could lead to a shutdown of the Strait of Hormuz, a narrow waterway separating Iran from the Arabian Peninsula through which roughly 40% of the world’s traded oil is shipped.
