From Jomana Karadsheh

Saif al-Islam was caught by revolutionary fighters after 15 days of pursuit in the area between the southwestern oasis town of Obari and southern town of Sabha, military commanders in Tripoli told CNN.

The 39-year-old, one of the most-wanted elements of the former regime, has now been taken to the city of Zintan in the Western mountains, Zintan fighter Hassan al-Jwaili told CNN.

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

Libya statement on Saif Gadhafi's capture

Saif Gadhafi arrested in Libya

The International Criminal Court in the Netherlands confirmed the arrest. The court wants Saif al-Islam Gadhafi for alleged crimes against humanity, including murder, committed during the uprising.

Chief prosecutor Luis Moreno-Ocampo said it was "good news" that he had been arrested.

"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 Gadhafi to justice, an ICC spokeswoman said Saturday.

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"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.

Outbursts of celebratory gunfire, the honking of horns and cries of joy could be heard in Tripoli as reports of his capture spread.

Othman Mliegta, commander of the Al Qa'aq brigades, said he had been told that Saif al-Islam was slightly injured in the clashes that took place when the fighters attempted to capture him but is in good health.

A picture released by Libya's National Transitional Council purportedly of Saif al-Islam appeared to show him half-lying on a low bed with bandages wrapped around the fingers of his right hand.

A military commander from Zintan, Fathi Al-Ayed, told CNN that Saif al-Islam's injuries had been sustained in previous clashes rather than the firefight that led to his capture in the early hours of Saturday.

Al-Ayed, who was in Obari at the time, said fighters from the Zintan Brigades had been following a vehicle convoy. As they approached, the convoy tried to flee, firing on the fighters, who returned fire.

When the convoy was eventually stopped, Saif al-Islam was arrested along with three other people, Al-Ayed said. All four were taken to Zintan.

Mliegta said those with Saif al-Islam Gadhafi when he was caught did not include his father's former intelligence chief Abdulla al-Sanussi, also wanted by the ICC.

Said to have played a major role in the bloody crackdown on the uprisings that began in Libya in February, Saif al-Islam was named in an Interpol arrest warrant in September.

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His father was killed last month near Sirte after his capture by forces loyal to the National Transitional Council.

Asked about guarantees of Saif al-Islam Gadhafi's safety, Mliegta said he would be treated in the same way as any other detainee.

National Transitional Council military liaison Abdelrahman Busin told CNN that any injuries Saif al-Islam had sustained would be treated.

There was still some secrecy over his movements, Busin said, but he could guarantee Saif al-Islam's human rights would be respected if he is handed over to the authorities in Tripoli.

It might be several months before a trial could be held but they were keen to keep him in Libya, he said.

Giving his reaction to the news of the arrest, he said: "I think the Libyan people can finally actually breathe a big sigh, finally relax to some extent, because he has been threatening to come back with revenge for some time now. So, it's a close for many, many people."

Military commanders told CNN they want the National Transitional Council to ensure Saif al-Islam is tried in their country.

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There are questions as to whether Libya would be able to give former regime members a fair trial.

However, the deputy minister of justice told CNN Friday the country does have the necessary judicial system in place.

ICC spokeswoman Florence Olara said: "We are in touch and coordinating with the Libyan ministry of justice to ensure that any solution with regards to the arrest of Saif al-Islam Gadhafi will be in accordance with the law."

Moreno-Ocampo, the ICC prosecutor, said previously that if Saif al-Islam Gadhafi was brought before the ICC in the Netherlands, he would "have all the rights and be protected," and would be allowed to present a defense.

NATO, which protected Libyan civilians under a U.N. mandate this year, said Saif al-Islam faces crimes against humanity charges in a conflict that "caused the Libyan people so much suffering."

"We trust that the Libyan authorities and the International Criminal Court will ensure that justice runs its course, so that the new Libya can be built on the rule of law and respect for human rights," NATO spokeswoman Oana Lungescu said.

Once seen as a possible successor to his father and an advocate of reform, Saif al-Islam Gadhafi became a vocal defender of his father's brutal regime.

His whereabouts had been unknown for months. At the end of August he made a call to Syria's Rai TV, in which he said he was speaking from a suburb of the capital, Tripoli, and urged Libyans to rise up against the rebels.

Saif al-Islam, whose mother is Gadhafi's second wife Safia, is the second-oldest son of the late strongman. He was educated at the London School of Economics and speaks fluent English.