Muammar Gaddafi could have an underground escape route from his military compound to Tripoli International Airport, an engineer who worked on plans to renovate its infrastructure told Channel 4 News.

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Although his actual whereabouts are unknown, it is widely believed that Gaddafi is holed up in Bab al-Azizya, the large military base located some 26km (16 miles) from the airport.

The engineer, John, an Irish national who fled Libya in February when the uprising reached Tripoli, told Channel 4 News that designs were in place over a year ago to create a subterranean road directly underneath the main highway that leads from the airway to the base and beyond, which could only be used by military vehicles.

"Gaddafi's people wanted the underground road so that military vehicles wouldn't get mixed up in civilian traffic. It also meant that access to and from the airport was easy for top officials when they were in Tripoli," he said.

He said that the company he worked for did not win the contract for the project, and was unsure of whether the project was ever completed.

He added, however, that "given the amount of time that has elapsed, and knowing that the project was seen as a priority, in all likelihood it was built".

The engineer also visited Bab al-Azizya in the southern suburbs of Tripoli several times to look at renovating the compound's underground bunkers.

The Libyans were keen to modernise the bunkers, which were 5-6m below ground level and could hold vehicles, which they felt contained outdated technology.

"It was clear that they had not been lived in or maintained for a long time. The computers and such were old, but the infrastructure was sound, and there was a network of labyrinthine passageways, fully functioning generators and up-to-standard living quarters, possibly for several hundreds of men," he said.

He added that government officials wanted the bunkers to be fitted out with state-of-the-art German technology to replace the existing ageing installations.

Earlier, the Telegraph quoted staff at Tripoli's Rixos hotel who said that Gaddafi was moving around Tripoli in secret tunnels.

"The dictator did not use the hotel's entrance and was not seen in its corridors or lobbies, which were full of reporters at the time. Staff at the (hotel) said there was a underground tunnel from the hotel to Bab al-Aziziya, which is about half a mile away on an adjacent plot of land," the paper writes.

Bab al-Azizya - Getty

Bab al-Aziziya has acted not only as a heavily fortified bolthole for Gaddafi since the uprisings began, but also as the symbol of the Libyan leader's defiance against the West.

It was here that his former residence was partially destroyed by American bombs in 1986, retaliatory strikes for the bombing of a Berlin nightclub frequented by US soldiers, two of whom were killed.

The strikes destroyed Gaddafi's living quarters and killed his adopted daughter Hanna, but the leader survived uninjured.

The building has not been rebuilt and has been renamed House of Resistance. In front of it stands a giant, gold sculpture of a clenched fist squeezing an American plane, as seen in the background of Gaddafi's television broadcast in February.

A three-storey administration building in the complex was also attacked in March, when a Libyan air force pilot crashed his jet into a building in what was thought to be a kamikaze-style attack.

Rebels claimed that Gaddafi's son Khamis died from injuries sustained in the attack, but he later appeared in public apparently unscathed.

Kim Jong-il

In 2009, a prominent defector from North Korean dictator Kim Jong-il's regime claimed he also had a network of secret tunnels as an escape route in case of emergency.

Hwang Jang-Yop, a former secretary of the North Korean Workers Party, said: "About 300m below ground in Pyongyang, there exists a second underground world which is different from the subway level."

The tunnels stretch for some 40 to 50km around Pyongyang linking to Nampo and Sunchon, Hwang said.