(Adds details, NTC comments, moves dateline to TRIPOLI from TUNIS)
By William Maclean
TRIPOLI, Sept 10 (Reuters) - Libya's provisional government chief, Mustafa Abdel Jalil, arrived in the capital Tripoli on Saturday for the first time since his allies chased Muammar Gaddafi out of the city, the provisional government said.
Abdel Jalil, chairman of the National Transitional Council (NTC), has been running the provisional administration from the eastern city of Benghazi, cradle of the revolt that overthrew Gaddafi in late August.
"He has returned. It is a historic moment," NTC spokesman Jalal al-Gallal told Reuters. "He will meet his leadership team and the full NTC to start the next stage of building a new Libya."
Live pictures on Al Jazeera television showed Abdel Jalil -- Gaddafi's former justice minister who defected at the start of the six-month civil war -- arriving in the city to the cheers of scores of his supporters waving NTC flags.
The arrival is a significant boost to the credibility of both Abdel Jalil and his new government.
Libya's new leadership said last month it would set up a provisional government in Tripoli as part of its plans to build up democratic institutions in the country after the revolt.
The NTC has said it will complete its move to Tripoli from Benghazi by the end of next week -- though previous forecasts have been followed by delays.
Some of that hesitation seems to stem from long-standing regional rivalries and from a sense that Tripoli -- run by rebel brigades that swept in from towns and provinces eager for a share of power -- may not be a safe place for every official.
The NTC's "timetable", which sets out plans for a new constitution and elections over a 20-month period, should start once the NTC declares Libya's "liberation".
It has yet to do so and it is unclear exactly how the disparate groups which have taken over the country will define what constitutes "liberation".
Another NTC spokesman said Abdel Jalil had a crucial role to play in unifying Libya after the war.
"All Libyan people agree on his leadership and I hope his coming to Tripoli will give a boost to efforts to normalise Tripoli and to normalise Libya," Mahmoud Shammam told Reuters. (Additional reporting by Mohammad Ben Hussein in Tripoli and Barry Malone in Tunis; Writing by Barry Malone; Editing by Peter Graff)