Global crude oil prices rose for the sixth straight week, after top producers Saudi Arabia and Russia extended supply cuts through September, adding to undersupply concerns. It is the longest streak of weekly gains this year. Brent crude oil futures have risen 17 percent and WTI by 20per cent in the last six weeks.

Brent ended to week at 86.24 dollars a barrel on Friday, while the US crude closed at 82.82 dollars a barrel. Both benchmarks hit their highest levels since mid-April on Friday.

Saudi Arabia on Thursday extended a voluntary oil production cut of 1 million barrels per day to the end of September, keeping the door open for another extension. Russia has also elected to reduce its oil exports by 300,000 barrels per day next month. UBS said Brent prices may touch 90 dollars per barrel in the coming months.