TRIPOLI, Libya — Powerful militias aligned with the Islamist-dominated parliament deployed in the Libyan capital Thursday, raising the specter of an all-out war with forces loyal to a renegade former general who wants the legislative body disbanded.

Known collectively as the Libya Central Shield, the militias from the western city of Misurata were heeding a call by the head of parliament, Nouri Abu Sahmein, to protect Tripoli after gunmen loyal to the ex-general, Khalifa Hifter, stormed it Sunday.

It marked the first time the Libya Central Shield has deployed to Tripoli since November, when its fighters opened fire on peaceful protesters outside their base, sparking clashes that left more than 40 dead and hundreds wounded.

The group’s main rivals, the Qaqa and Sawaiq brigades from the western city of Zintan, have allied with Hifter, threatening a confrontation in Tripoli between two of the country’s most powerful militia forces.

The deployment is the latest development in a long-brewing crisis that ignited Friday when Hifter led a fierce assault on Islamist militias in the eastern city of Benghazi. More than 70 were killed in the fighting, the heaviest in the country since the 2011 revolt that deposed autocrat Moammar Gadhafi.

Since then, Hifter has steadily picked up support from current and former military officers, political figures, civil society groups, and the militias that dominate many Libyan cities. He has called for parliament to be dissolved and an emergency government appointed to oversee the transition until parliamentary elections scheduled for June 25.

The growing support for Hifter’s self-declared Libyan National Army stands in contrast to deepening divisions between parliament and the interim government.

On Thursday, the government criticized Abu Sahmein for ordering the Misurata militias into the capital, saying their presence “threatens the safety of citizens.” It also accused parliament of “not bothering to reply” to a proposal earlier in the week calling for the body to suspend activities until the election.

Libya’s political transition has been unraveling over the past several months. Many point to the imposition in November of a draconian law that expelled many figures who once worked for the Gadhafi regime, even though they later became dissidents and participated in the 2011 revolt.

The government also has failed to create a unified military or a strong police force from the scores of well-armed militias that emerged from the revolution, and it has done little to halt the killings of former army and police officers, judges, activists and others at the hands of radical Islamist groups. Meanwhile, half of Libya’s oil production has been shut down by a militia leader in the eastern city of Ajdabiya. He seeks to split the country into three self-governing parts along tribal lines.

One of the latest triggers for the ongoing crisis was the appointment of Ahmed Matiq, a Misurata businessman, as prime minister about two weeks ago in a disputed vote.

In addition, last summer’s events in neighboring Egypt, in which the military ousted President Mohammed Morsi, an Islamist allied with the Muslim Brotherhood, also have had a polarizing effect on the political narrative in Libya. A growing number of Libyans came to see parliament as dominated by Islamists. Their opponents increasingly used rhetoric that made little distinction between Brotherhood-like political groups in Libya and Islamist militias.

“The Muslim Brotherhood and al-Qaida want Libya to be an emirate,” said Attiyah Omar al-Mansour, a former Libyan air force brigadier general who fought with Hifter in the 2011 civil war and describes him as a “friend and comrade.”

The Libyan government views Hifter’s operation as a military coup and likens him to Gen. Abdel Fattah el-Sissi, who ousted Morsi and is widely expected to win Egypt’s presidential election next week. Islamist militias, such as Ansar al-Sharia, have portrayed Hifter’s offensive as a “war on Islam.”

“In Libya, we’re seeing things falling into place along this Islamist and non-Islamist narrative, but in reality it’s a lot of diverse interests,” said Issandr El Amrani, director of the North Africa project at the International Crisis Group. “It is a very fragmented country that doesn’t usually explain itself in terms of a bipolar arrangement.”

“Some kind of political bargain is necessary,” he said. “The transition process that started in late 2011 is the only thing that’s keeping the state together in Libya.”