Brent North Sea crude for September delivery shed 1.
91 dollars to 115.99 dollars per barrel in electronic deals.
New York's main contract, light sweet crude for September delivery dropped 1.73 dollars to 118.29 dollars a barrel.
The Baku-Tbilisi-Ceyhan (BTC) pipeline at Refahiye in eastern Turkey has been on fire since the blast on Tuesday and was expected to be closed for about two weeks.
The separatist Kurdistan Workers' Party (PKK) said on Friday that the explosion was "an act of sabotage" by its militants, according to a report on the website of the Firat news agency which is close to the rebels.
World oil prices had rebounded back above 120 dollars on Thursday on news that the pipeline carrying crude from Central Asia to the West would remain shut for about 15 days.
The BTC was inaugurated in 2006, carrying oil from the Caspian Sea fields to Turkey's Mediterranean port of Ceyhan, from where tankers transport the crude to Western markets.
Despite modest price gains