At least 18 people were killed in fierce clashes Friday between Islamist groups and forces loyal to the army and an ex-general in Libya's second city of Benghazi, hospital sources said.

Benghazi Medical Centre said the dead were mostly soldiers and civilians fighting alongside the army in the central district of Al-Majouri.

On Wednesday, forces of retired general Khalifa Haftar, backed by army units, launched what he called an operation to "liberate" Benghazi from Islamist militias that control the eastern city.