Tony Karon writes: “I fear this looks like a civil war”, one Libyan rebel commander from Misrata told the Associated Press, in the wake of a fierce firefight between rival militia factions using heavy weapons in broad daylight in Tripoli on Tuesday. Four fighters were reportedly killed and five wounded in the clash ignited by the attempts of a Misrata-based militia to free a comrade detained by the Tripoli Military Council on suspicion of theft. But such clashes have become increasingly common in the Libyan capital over the past two months, as rival militias stake out turf in the power vacuum caused by the collapse of the Gaddafi regime. And while leaders on both sides of Tuesday’s clash were eventually able to broker a cease-fire, the deep fissures of tribe, region, ideology and sometimes even neighborhood that divide rival armed groups persist —and there’s no sign yet of the emergence of a central political authority with the military muscle to enforce its writ.

The residents and militias of Tripoli have been trying for months to persuade the Misrata and Zintan fighters who stormed the capital to topple the regime to go back to their home towns, but those fighters are staying put—and are accused of harassing the locals. They see themselves as the ones who shouldered the greatest burden in the battle to drive out Gaddafi, and they are suspicious of edicts by the National Transitional Council (NTC), which they see as self-appointed interlopers from Benghazi (the NTC’s recognition by the West and Arab governments as Libya’s legitimate government notwithstanding). The fighters of Zintan and Misrata are in no hurry to subordinate themselves to a national army led by returned exiles and a government of which they’re wary; nor are they willing to accept the authority of the Tripoli Military Council headed by the Islamist Abdel Hakim Belhadj, despite his endorsement by the NTC. Mindful of the political power that flows from being armed and organized, and determined to leverage that into a greater share of power and resources for the regions and towns they claim to represent, the regional militias are in no rush to give up their control of prized political real estate. They’ve ignored the Dec. 20 deadline to leave Tripoli. And, when NTC-backed armed groups tangle with them, as happened with the New Year’s Eve arrest of some of their men, they’re willing to fight.