The United States pressed Libyan opposition leaders Friday to shore up any cracks in their front against Moammar Gadhafi's regime, after the mysterious killing of a top rebel commander raised the specter of infighting among the forces hoping to replace four decades of dictatorship with democracy.
State Department spokesman Mark Toner said the circumstances of Abdel-Fattah Younis' death Thursday were still unclear. He called it an additional challenge for the opposition Transitional National Council, which is locked in a civil war against the Gadhafi regime, and said American diplomats in rebel-held eastern Libya were trying to determine how Younis was killed.
"What's important is that they work both diligently and transparently to ensure the unity of the Libyan opposition," Toner told reporters.
The plea for unity comes as questions swirl about the culprits and motives behind the killing of Younis, who was Gadhafi's feared security chief before defecting to give the rebels a major boost.
Younis was summoned to the rebel stronghold of Benghazi because of alleged links among his family to the Gadhafi regime. After leaving the front lines, attackers shot him, slit his throat, set fire to his body and dumped it outside Benghazi, his nephew Hisham al-Obaidi told The Associated Press.
The death has spread confusion in Libya and dilemmas for Western governments.
The U.S. and dozens of other nations have recognized the council as the legitimate leadership of Libya, despite some lingering questions about the composition of the opposition and its intentions. The council has spoken firmly of its plans to set up a democratic state guided by the respect for human rights and the rule of law, but Younis' death raises the possibility that internal splits could undermine its forces or lead the revolution in new and unpredictable directions.
Toner said the government must lead according to its principles. "What's important is that they adhere to their pledges and commitment to unity and representation of all the Libyan people," he said.
The rebels will miss Younis' military expertise and leadership, Toner said. He said Younis' death adds to the challenges facing the once-ragtag coalition of cities and tribes that has been able to conquer much of Libya with the assistance of NATO air forces. But he added that it was important that focus remain on the ultimate goal: getting Gadhafi to leave power.
In Libya on Friday, Younis' killing remained almost entirely unexplained. The head of the rebel National Transitional Council, Mustafa Abdul-Jalil, blamed "gunmen" and said one man had been arrested, he didn't say what might have motivated the killers.
American officials said they've heard conflicting stories about what might have happened _ from Younis being killed by his own guards to being shot at a checkpoint. Another theory circulating is that Younis was turned over to Gadhafi's forces and killed. But the truth remained elusive, hindering an American response, said the officials, who spoke on condition of anonymity because of the uncertainty of the situation.
Younis' death could be a propaganda coup for Gadhafi's forces, even if they did not kill him. Younis was among the army officers who joined the 1969 coup that brought Gadhafi to power, and remained the dictator's ally for more than 40 years before joining the uprising in February. Still, his history means he likely had many enemies among the rebels.
One U.S. official expressed optimism that Younis' death wouldn't send the rebels "into a spiral." The U.S. believes the opposition should be able to recover and move on, once the facts are made clear, the official said.
Associated Press writer Matthew Lee contributed to this report.