Colonel Gaddafi's son Saif al-Islam has been captured, officials from Libya's interim government have said.He was arrested near the town of Obari in the south of the country, the officials said.The former leader's son is the last key member of the Gaddafi family to be captured or killed.Saif al-Islam, 39, is wanted by the International Criminal Court for alleged crimes against humanity during the uprising against his father.The National Transitional Council's (NTC) justice minister Mohammed al-Allagui said Saif al-Islam had been detained along with a number of bodyguards, Reuters news agency reported.Officials said Saif al-Islam was being taken to Zintan in the north of the country.Gaddafi's son was in good health, the justice minister is reported to have said.A commander of the Zintan brigades, allied to the NTC, told a news conference that Saif al-Islam was captured as aides were trying to smuggle him out to neighbouring Niger, the Associated Press news agency reported.Saif al-Islam had been on the run since NTC forces took the capital, Tripoli, in August.Colonel Gaddafi himself was killed on October 20 after being captured during the final battle for his hometown, Sirte.The interim government in Libya has launched an inquiry into how he died.CelebrationsThe BBC's Rana Jawad in Tripoli says Saif al-Islam's capture is a very significant moment for Libyans.They came to see Saif al-Islam as the heir apparent, as a younger version of his father due to his rhetoric during the uprising, she says.However, at one time he was considered one of the more liberal of Col Gaddafi's sons and was courted in the West.Celebrations erupted on the streets of Tripoli shortly after the news of his arrest emerged.Our correspondent heard people hooting car horns, waving flags and firing guns into the air.Saif al-Islam has been reported captured before. In August, rebel forces announced his arrest as they took control of Tripoli - only for him to appear in front of cameras to disprove it.