Libya's recognized government said it forced a tanker from delivering fuel to its rival administration, diverting the vessel to its own territory by threatening an air attack on it.
The tanker Anwaar Afriqya was approaching the port of Misrata, but diverted to Tobruk, a port official at the latter said on Monday.
"Our planes are forcing an oil tanker to sail to Tobruk after it had been on the way first to Misrata," Saqer al-Joroushi, air force commander for recognized Prime Minister Abdullah al-Thinni
, told state news agency Lana.
Libya's recognized government works from a headquarters in the east of the country since the summer when rival forces under the banner Libya Dawn took over the capital Tripoli and installed their own self-proclaimed government.
The latest tanker incident has underscored how increasingly Libya's oil infrastructure
is at the heart of conflict that Western powers worry is dragging it closer to a civil war.
Forces loyal to Thinni's government carried out air strikes earlier this month on a Greek-owned oil tanker and a fishing vessel carrying fuel in an escalation of the conflict.
Tripoli's rival oil minister, Mashallah Zwai, said late on Sunday a tanker loaded with 24,000 tonnes of fuel oil was forced to divert to Tobruk while en route to Misrata, which is allied with the Tripoli forces.
"We were contacting the captain until late at night on Jan. 24 to convince him to continue his journey to Misrata to discharge the fuel, but the captain said he had been told in repeated phone calls to move to Tobruk or get bombed," Zwai's oil ministry said in a statement.
This month two crewmen were killed in the airstrike on a Greek-owned oil tanker moored
off the port of Derna, drawing international condemnation and stoking concerns about growing violence.
While the Tripoli government is not recognised by world powers, it controls ministries in the capital as well as ports and airports in western Libya, making it difficult for oil buyers and shippers to avoid dealing with it.
Each side has appointed its own oil minister and head of the state-owned National Oil Corp. Armed forces allied to Tripoli tried to seize the eastern ports of Ras Lanuf and Es Sider, forcing both to shut down.
(By Ulf Laessing; Additional reporting by Jonathan Saul; editing by Patrick Markey and William Hardy)