By Ghaith Shennib and Feras Bosalum
TRIPOLI/BENGHAZI, Libya (Reuters) - Libya's army chief of staff resigned on Sunday after clashes in the eastern city of Benghazi the previous day in which 31 people were killed, national assembly sources said.
In a closed-door meeting, Yussef al-Mangoush told the General National Congress, Libya's highest political body, that he would no longer continue in the job and the assembly accepted the resignation, three members told Reuters.
"Yussef al-Mangoush has told the congress he is no longer willing to continue the journey," one politician told Reuters in a mobile phone message. Two other sources confirmed the resignation.
The congress picked Mangoush's deputy, Salem al-Gnaidy, to fill the position until a new army chief is picked, one member said. Speculation has been rife for months about Mangoush's fate amid an increase in violence.
On Saturday, fighting broke out at the headquarters of the Libya Shield brigade in Benghazi when protesters demanded the disbanding of militias made up of former rebels.
Resentment has been building for months over the myriad militias' continued existence nearly two years after the fall of Muammar Gaddafi, not least after militiamen laid siege to ministries in Tripoli last month to force their will on the national assembly.
But the central government, whose own forces are too weak to maintain security in a country awash with weapons, has found itself having to co-opt or license some of the most powerful militias to maintain even a semblance of order, while shutting down some others.
Order was only restored in Libya's second city on Saturday when special forces seized the compound of Libya Shield, which said it was operating with official approval.
Libya Shield is an umbrella group of brigades with bases in Benghazi, cradle of Libya's 2011 uprising.
Earlier, Ali al-Sheikhi, spokesman for the army chief Of staff, said any decision on disbanding the brigades could only be taken by the national assembly, but that national army colonels had been ordered to take control of these bases in Benghazi. "This is what the people want," he said.
The planned to seize the bases was confirmed by Abdullah al-Shaafi, spokesman for the government's Benghazi security operations room, but it was not immediately clear when this would happen or whether the brigades would cooperate.
"What army can take control?" said Ismail Salabi, a Libya Shield commander. "There is no army but Libya Shield."
Thirty-one people were killed and more than 100 wounded in Saturday's fighting in Benghazi, a doctor at the city's al-Jalaa hospital said. A military source said at least five soldiers from the national army were among them.
Anger at the militias surged in Benghazi last September after the killing of the U.S. ambassador and three other Americans in an attack on the U.S. mission there.
A copy of a congress resolution passed on Sunday, seen by Reuters, said the assembly urged the government to take "all necessary steps to stop the presence of unauthorized armed groups".
It also called for a plan to be issued in two weeks for how former rebel fighters would be integrated into the army, as individuals.
(Reporting by Feras Bosalum in Benghazi and Ghaith Shennib in Tripoli; Writing by Marie-Louise Gumuchian; Editing by Kevin Liffey)