By Satish Jacob BBC correspondent in Delhi

The Indian capital Delhi now has its own metro train as a result of a massive civil engineering project

Many tunnels will run 17m below the surface

The Deputy Prime Minister, Lal Krishna Advani, signalled the start of the first trial run of the subway train and was met with celebrations and fanfares.

The first section of the subway across north Delhi will open in December but trains will be running on a trial basis until then.

Trials of the service, during the next few months, will be conducted along an 8.3 km route, connecting eastern Delhi's Shahdara to north-central Tis Hazari.

A number of leading citizens were on hand to see the four-coach train, built in South Korea, roll out for its first trial run.

Costly venture

The construction of the metro began in 1998 and the entire network is expected to open in three years' time.

It is hoped the metro will reduce traffic problems

Residents in Delhi are hoping the massive traffic congestion on the roads, where over 12 million people and four million vehicles jostle for space, will improve dramatically.

Correspondents say it is also hoped that the metro will cut pollution in Delhi by around 50% when the metro's first phase, stretching over 62km, is completed in 2005.

Work on other sections is progressing at a furious pace.

The first phase of the metro system is being built at a cost of 80 billion rupees ($1.6b).

Massive undertaking

Analysts say when completed, this stretch of the metro will do away with the need for nearly 2,600 buses or 33 lanes of private motor cars.

Children of metro workers look on in delight

Delhi state Chief Minister, Sheila Dikshit, said: "In the years to come, the metro rail is going to change not only the face of Delhi and its transport system, but also the capital's work culture."

Large parts of Delhi are being dug up and a tunnel, which would run 17 metres below the surface, is being carved out by the same equipment used to build the English Channel tunnel.

The metro is one of the biggest infrastructure projects undertaken in India since the British built New Delhi.