Armed men exploded a pipeline pumping crude oil to Es Sider port, cutting Libya’s output by up to 100,000 barrels per day (bpd), military and industry sources claimed.
The state-run National Oil Corporation (NOC) said in statement output had been reduced by 70,000-100,000 bpd. The cause of the blast was unclear, it added.
The attackers arrived at the site near Marada in two cars and planted explosives on the pipeline, a military source said.
Pictures purportedly showing a huge cloud from the blast in central eastern Libya circulated on social media.
The damage was still being assessed, one oil source said. Oil prices rose on the report.
Islamic State fighters had a presence in the area until government forces expelled them from their main stronghold in Sirte a year ago.
The operator of the pipeline is Waha, a subsidiary of the NOC and a joint venture with Hess Corp, Marathon Oil Corp and ConocoPhillips.