After Gaddafi son, spy chief run to ground - Reuters Africa

(Adds Senussi surrounded, possibly captured)

* Gaddafi intelligence chief said surrounded

* Day after capture, Saif al-Islam held in militia stronghold

* Fighters say will hand over only when new govt formed

* Custody tussle over Gaddafi son may drag on

By Alastair Macdonald

TRIPOLI, Nov 20 (Reuters) - A day after Muammar Gaddafi's son was captured by Libyan fighters, the ousted leader's intelligence chief Abdullah al-Senussi was said to be surrounded nearby at a remote desert homestead and negotiating his surrender.

The arrest of the other survivor of the old regime who is wanted at The Hague for crimes against humanity would crown a momentous couple of days for a new government that is still in the process of formation, and also pose immediate tests of its authority - both over the militias and with the world powers.

A commander of former rebel forces nominally loyal to the National Transitional Council (NTC), General Ahmed al-Hamdouni, told Reuters that his men, acting on a tip, had found and surrounded Senussi at a house belonging to his sister near the town of Birak, about 500 km (300 miles) south of Tripoli and in the same general area as Saif al-Islam was seized on Saturday.   Continued...