BENGHAZI, Libya (Reuters) - Eastern Libyan forces attacked an air base in the central region of Jufra on Thursday, killing at least two people according to a force spokesman and a medical source, hours after factional fighting flared in the capital Tripoli.

A U.N.-engineered Government of National Accord (GNA) that was installed in Tripoli last year has struggled to assert its authority over various armed groups in the capital alone, let alone elsewhere in sprawling, oil-producing Libya.

The eastern-based Libyan National Army (LNA) has clashed with rival brigades in the Jufra area in recent weeks, accusing them of trying to attack Mediterranean coastal oil ports that the LNA took control of last September.

LNA spokesman Ahmed al-Mismari said Thursday’s military strike, in which 13 people were also wounded, was aimed at “immobilizing the enemy before an expected attack on the ports”. Forces that control the targeted air base could not immediately be reached for comment.

The battles around Jufra have raised fears of a broader escalation between military alliances based in eastern and western Libya that have been involved in intermittent warfare since 2014.

The LNA, led by prominent military commander Khalifa Haftar, has been extending its control to the west and has threatened to march on Tripoli.

Haftar, who is aligned with a self-styled government based in eastern Libya, has opposed the U.N.-backed GNA that arrived in Tripoli, in the country’s west, last year.

Some of the capital’s many armed groups are still loyal to a third, self-declared government led by Khalifa Ghwell.

In the latest challenge to the GNA, Mahmoud Zagal, a military commander allied to Ghwell, announced on Thursday the formation of the “National Guards”, which he said would be used to secure state institutions and diplomatic missions.

Zagal’s force arrived in Tripoli on Wednesday from Misrata, Ghwell’s home city, in a convoy of several dozen vehicles, triggering heavy clashes with an armed group loyal to the GNA in the southern districts of Salaheddin and Abu Salim.

Most diplomatic missions evacuated from Tripoli after heavy battles in 2014, though the Italian and Turkish embassies reopened last month.

Libya’s factional chaos dates to the 2011 uprising that toppled veteran dictator Muammar Gaddafi.