At least 12 Libyan soldiers have been killed and 45 more wounded in fresh clashes with Islamist fighters near the airport of the eastern city of Benghazi, according to local sources.

The city was quiet by Friday evening, residents said.

Special army forces allied to brigades of renegade former General Khalifa Haftar have been fighting Islamist brigades in Benghazi, including Ansar al-Sharia, accused by the US of killing its ambassador to Libya in 2012.

A hospital medic said 12 soldiers were killed and 45 wounded in Friday's clashes.

Mohamed El Hejazi, a spokesman for Haftar, said the Islamist offensive on the Benina airport, located outside Benghazi, had been stopped with the help of warplanes and helicopters.

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"They tried taking the airport, but we won't allow this," he said.

The Islamist groups have launched a new offensive to seize Benghazi's military and civilian airport, the last government bases in the port city.

Al Jazeera's Mahmoud AbdelWahed, reporting from Tripoli on Thursday, said four separate suicide attacks targeted the Benina airbase, killing at least 40 soldiers loyal to Haftar and wounding dozens more.

"The airbase houses heavy weaponry and is crucial for the militias as they attempt to seize control of Benghazi," he said.

The Shura Council of Benghazi Revolutionaries said it carried out Thursday's attack in conjunction with the Libya Shield brigade and Ansar al-Sharia.

Chaos has gripped the oil-producing North African nation three years after the overthrow of long-time ruler Muammar Gaddafi.

The Islamists have already overrun several army bases in Benghazi.

Western powers are concerned that Libya will become a failed state as a weak central government cannot control competing militia who helped topple Gaddafi but now use their weapons to dominate politics or a share of the country's vast energy resources.

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.

Source: Al Jazeera and agencies