Updated

Libya's Prime Minister Ali Zidan on Thursday called on militias to evacuate their buildings and headquarters and join government security forces, vowing that his government will take a hard-line stand against any armed group that tries to hijack control of any part of the nation.

Since the fall of Libyan dictator Moammar Gadhafi in 2011, armed groups, including rebels who battled Gadhafi's forces during eight-month civil war, have posed a challenge to transitional authorities struggling to transform them into a unified national military and police force.

During a police graduation ceremony in Tripoli, Zidan said the state "will not be lenient and we will not permit hijacking of Tripoli or Benghazi or any other city."

On the one hand, the Libyan government heavily depends on security provided by commanders of powerful militias, such as Rafallah Sahati and Libya Shield. President Mohammed el-Megarif has labeled them as "legitimate" forces.

But other militias, such as Ansar al-Shariah, are labeled as outlaws. Ansar Al-Shariah is suspected of carrying out the deadly attack on the U.S. mission in Benghazi on Sept. 11 that killed four Americans, including U.S. Ambassador to Libya Chris Stevens.

Militias, however, often act with impunity, running their own prison cells, making arrests and taking confessions in total absence of state control and oversight.

Libyans have been staging protests and sit-ins demanding that authorities label all militias illegal. The protesters want militia commanders and their fighters to integrate into the Libyan army as individuals. If they integrate into the army as groups, they say the fighters will maintain their loyalty to their militia commanders.

Libya's newly appointed Interior Minister Ashour Shwayel says the number of policemen, including those who are inactive, is 120,000 and thousands are to join in coming weeks.

Zidan's vow to stand against militia came as a video circulated on social networking sites purportedly showing a militia holding a group of Christian Egyptians. The video depicts a group of detainees with shaved heads and a bearded young man in a military jacket who says nearly 100 Coptic Egyptians are being held for allegedly spreading Christianity in Libya. The video, posted on The Seventh Day news website, showed bibles and Christian books next to the detainees.

The authenticity of the video could not be independently confirmed.

Hundreds of thousands of Egyptians are working construction and trade jobs in Libya, a nation of 6.5 Muslims with no significant religious minority.

Egypt's foreign ministry said its embassy in Libya was investigating the allegation.

There was no immediate comment from the Libyan government.

Earlier this month, four foreigners — an Egyptian, South Korean, South African and Swede, who had an American passport — were arrested, detained and accused of spreading Christianity. The Libyan police chief behind that case, Abdel-Salam el-Barghathi, said that the new case was not linked to the one he handled. While not in charge of the most recent case, he claimed that the claim that nearly 100 Christians were being detained was an exaggeration. He did not elaborate.