Tripoli, Libya (CNN) -- Libyans celebrated late into the evening Saturday the reported capture of Moammar Gadhafi's son, Saif al-Islam, nabbed in a desert gunbattle after an 18-day stakeout.





Senior Libyan military officials said they believe the potential Gadhafi successor was trying to make his way to neighboring Niger, where a brother, Saadi, was granted asylum.





Revolutionary fighters caught the man wanted by the International Criminal Court between the southwestern oasis town of Obari and southern town of Sabha, military commanders in Tripoli told CNN.





The 39-year-old, the last Gadhafi fugitive, was taken to the city of Zintan in the western mountains. Top officials in the town rejoiced over the development.





Saif al-Islam had been on the run since shortly after the fall of his father's Bab al-Aziziya compound in the capital in August.





"I hope that this is the beginning of a state of freedom, transparency and lawfulness," acting Prime Minister Abdurrahim El-Keib told reporters in Zintan. "In the name of the great nation, we would like to allay your fears and tell you that Saif and those who were with him will be tried fairly. They are ensured all their rights under the law. These are the same rights that our nation didn't have for 42 years."





The ICC in the Netherlands wants Saif al-Islam for alleged crimes against humanity, including murder, committed during the uprising this year.





But officials in Libya also indicated they would like to put Saif al-Islam on trial.





Although he held no high-level government office, Saif al-Islam was considered by ICC prosecutors to be Moammar Gadhafi's "unspoken successor and the most influential person with his inner circle," according to an arrest warrant issued in June.





The Gadhafi regime formulated a state policy that included quelling demonstrations by lethal force, attacking civilians and imprisoning hundreds, according to the warrant. Saif al-Islam "exercised control over crucial parts of the state apparatus, including finances and logistics and had the powers of a de facto prime minister."





ICC Chief Prosecutor Luis Moreno-Ocampo said the arrest was "good news."





"That is very important because we consider him -- the judges consider him -- the principal, with his father Moammar, of the crimes committed in Libya after February 13," he said. "He's arrested, he's alive, and now he will face justice and that is the most important news."





Moreno-Ocampo will travel to Libya next week to coordinate efforts to bring Saif al-Islam to justice, an ICC spokeswoman said Saturday.





Who is Saif al-Islam Gadhafi?





"The ICC has had indirect contact with Saif al-Islam Gadhafi through intermediaries during which they discussed what would happen if he surrendered. The last contact was 25 days ago," spokeswoman Florence Olara told CNN.





ICC spokesman Fadi el-Abdallah told CNN that Libya has an obligation to surrender Saif al-Islam to the ICC. If Libya wants to conduct a trial, it needs to submit a request to judges and show its legal system is capable of properly handling such a proceeding.





El-Keib emphasized that "we will deal with this under our legal system," but he said the country intends to communicate and work with the ICC.





"We'll get to a point where we can take care of this issue easily," El Keib said. "We definitely are interested in respecting the will of our people and also the national interests that we trust that the world will also appreciate."





Justice Minister Mohammad Al-Alagy said he doubts Libyan courts would want to try Saif al-Islam for crimes against humanity.





"We will weigh out the accusations against Saif Al Islam al-Gadhafi. Afterward, we will know what crimes to try him with. He's charged with killing and taking the nation's money and ... hiring mercenaries. Those are crimes the Libyan nation will currently try him for. We can't move ahead of ourselves with inaccurate accusations. We will move forward with this
The PM says what about Saif? What is Libya planning? Libya needs to submit what to the conduct trial? What does it need to submit? What did PM say?
"I hope that this is the beginning of a state of freedom, transparency and lawfulness," put Saif al-Islam on trial. a request to judges and show its legal system is capable of properly handling such a proceeding. a request to judges "I hope that this is the beginning of a state of freedom, transparency and lawfulness,"
question: The PM says what about Saif?, answer: "I hope that this is the beginning of a state of freedom, transparency and lawfulness," | question: What is Libya planning?, answer: put Saif al-Islam on trial. | question: Libya needs to submit what to the conduct trial?, answer: a request to judges and show its legal system is capable of properly handling such a proceeding. | question: What does it need to submit?, answer: a request to judges | question: What did PM say?, answer: "I hope that this is the beginning of a state of freedom, transparency and lawfulness,"