Up to 12 Libyan soldiers were killed and 60 wounded in a double suicide bombing and clashes in the port city of Benghazi on Thursday, medics said.
Four people were also killed in a separate attack by suspected Islamists on an army checkpoint in Qubah, east of Benghazi, hospital officials said.
Libya is being racked by violence as the armed groups which helped topple Moammar Gadhafi in 2011 turn their guns on each other in a struggle for the country's vast oil resources and political domination.
In Benghazi, special army forces allied to brigades of former general Khalifa Haftar have been fighting Islamist brigades including Ansar al-Sharia, accused by Washington of killing the U.S. ambassador to Libya in 2012.
Two cars loaded with explosives drove into an army checkpoint near Benghazi's civilian and military airport, killing three soldiers, Wanis Bukhamada, commander of army special forces in Benghazi, told Reuters.
Four soldiers were killed in clashes with Islamist militants in the same area, he said.
“The Majlis al-Shoura forces suffered big losses,” Bukhamada said, referring to a group of Islamists which has been trying to take the airport for weeks.
A hospital medic put the death toll at 12.
The Islamists have already overrun army bases in the eastern city, making the airport one of the last large government bases.
Clashes continued into the afternoon and air strikes could be heard. No more details were immediately available but Haftar's forces have used helicopters and war planes against the Islamists in the past.
Western powers worry Libya will become a failed state as a weak central government cannot control competing militia in a country awash with weapons.
The elected parliament has relocated to the remote eastern city of Tobruk after effectively losing control of the capital Tripoli, where an alliance of armed groups hold sway.
The new forces controlling Tripoli, led by brigades from the western city of Misrata, have helped install an alternative parliament and prime minister.