By William Maclean

LONDON (Reuters) - Resurgent violence in Tripoli shows Muammar Gaddafi's threat of a counter-revolutionary "volcano" in Libya is far from idle, with die-hard fighters, secret arms stashes and possibly tribal solidarity favoring his bid to cripple a rebel takeover.

For Gaddafi, staying alive and evading capture are the supreme immediate imperatives, for his sons are believed to lack the political clout to rally significant numbers of Libyans against rebel rule in the event of his death.

To that end, Gaddafi is likely to be counting on aides who are reputed to have built and maintained a network of tunnels under the city for use in the event of a threat to Gaddafi's rule, which has seen off several coup attempts over the decades.

His security experts will know the location of emergency arms stockpiles and may seek access to a research center near Tripoli said by a former U.N. inspector to stock uranium and other material that might be used for a nuclear "dirty bomb."

The UK-based Exclusive Analysis risk forecasting company said that the main terrorist threat emanating from Libya in the next six months was likely to be from Gaddafi loyalists.

It cited the case of a Libyan soldier who gave himself up to Tunisian authorities in Tunis, saying he had been sent by Gaddafi's army to bomb an Arab embassy in the capital.

Libyan state television has routinely accused Arab states Qatar and the United Arab Emirates of being "traitors" for supporting a rebel offensive seeking to topple Gaddafi.

GADDAFI NETWORKS PUT TO THE TEST

"A lot depends on the strength and effectiveness of his support network," said Ben Barry, a former British Army brigadier and now a land warfare expert at the International Institute for Strategic Studies in London (IISS).

"(Ratko) Mladic and (Radovan) Karadzic had good support, access to income and links to political extremists and organised crime. If Gaddafi has similar connections, he will be better able to make himself hard to find," he said, referring to Bosnian Serb leaders now at the Yugoslav war crimes court.

Gaddafi takes ostentatious pride in his record as a plotter and clandestine operator.

The Tripoli Museum on Green Square in the center of the city has for years displayed the venerable VW Beetle he used to travel around the country when secretly planning the 1969 putsch that toppled King Idriss.

Those reflexes may have dulled over the years, but Gaddafi, if he still has access to large amounts of money, may well be able to cause trouble by buying support from Libyan tribes.

His hometown of Sirte is heavily defended by members of his Gaddafa tribe, and the security situation in the southwest of the vast desert country is unclear.

OLD FEUDS MAY STIR

Alex Warren, of the Frontier MEA consultancy, said that old feuds in the south might revive in the collapse of any remaining law and order in coming weeks. The abundance of weapons now circulating throughout the country also boded ill.