The order to march on the capital came as Antonio Guterres, the UN secretary­ general, was in the city to push for a political solution that includes a national conference, due to be held on April 14, to agree a political road map including elections. He called for restraint and said there was no military solution to Libya’s problems, only a political one.  “There can’t be a national conference in these circumstances,” said Mr Guterres.

General Haftar’s self-styled Libyan National Army has already taken the town of Gharyan 90km south of Tripoli after a rapid sweep westwards across the vast North African oil-exporting country. In a video posted on the LNA Facebook page, the military man said: “To our army which is stationed on the outskirts of Tripoli. Today we complete our march … we are going to start shortly … We are coming to Tripoli, we are coming.” He told his forces not to open fire against civilians and anyone who lays down their arms.  Wolfram Lacher, a Libya specialist at the German Institute for International and Security Affairs, said: “Forget about the conference. The political process is dead for Haftar. For him now, it’s all or nothing. Either he takes Tripoli quickly or he suffers a devastating defeat because he cannot sustain his supply lines.”

He said Gen Haftar’s advance had already united militias from the capital and the nearby quasi-independent city of Misurata, which has its own formidable fighting force. Reuters news agency cited residents on Thursday night as saying armed forces from Misurata were already marching to Tripoli to take part in its defense.  The eastern strongman, who says he is opposed to Islamists of all hues, has vowed to remove “terrorists” from Tripoli. He enjoys the backing of Egypt and the United Arab Emirates, which are wary of the rise of any Islamist groups in regional politics. France also sides with Gen Haftar, whom it considers an important player in the fight against Isis and al-Qaeda in the Sahara.