NEW DELHI, INDIA - THOUSANDS of police and soldiers locked down India's capital on Thursday, bidding to keep Tibetan protesters away from the most sensitive leg of the protest-hit Beijing Olympic torch relay so far.

Tibet's government-in-exile under spiritual leader the Dalai Lama appealed for peaceful protests but authorities were taking no chances, deploying elite security forces and erecting barricades along the route.

Officials have already scaled back the relay and were keeping the route a secret amid fears thousands of India's huge community of Tibetan refugees will try to disrupt the event.

India is considered particularly vulnerable because it is home to more than 100,000 Tibetan refugees, including the Dalai Lama and radical youth groups.

Authorities said they were worried that activists might set themselves on fire in front of TV cameras.

'We have deployed three fire trucks along the route to meet any eventuality and any untoward incident,' a fire department spokesman said.

'We are carrying blankets and we have an ample supply of water,' a security official added. 'We cannot allow ugly scenes in front of dignitaries.'

Fears of severe disruption have already forced Indian officials to shorten the route, cutting it to a mere 2.3 kilometre jog along an avenue running from the presidential palace to India Gate.

The event is expected to kick off around 4 pm (1030 GMT), but officials were refusing to confirm the exact time.

About 1,000 protesters kicked off a rival torch relay in New Delhi, setting off from the mausoleum of Mahatma Gandhi, the champion of India's non-violent independence movement, and carrying a torch and chanting 'Free Tibet'.

A police spokesman said the march was unauthorised, and that police would 'look into it'.

The pro-independence Tibetan Youth Congress, which is taking a tougher line than the Dalai Lama, said it hoped to outsmart police and disrupt the relay.

'We have already made our plans,' the group's vice-president Dhondup Dorjee said. 'We are trying our best to get as close as possible to the torch.

'If we reach in front of the torch, we will ask the Chinese guard to shoot us down.'

Dozens of its members were detained by police overnight as the torch landed here from Pakistan, witnesses said.

But even if the group's plans to disrupt the relay are foiled, Dorjee said 'the impact has already been made' with the Games already overshadowed by the wave of international protests over Tibet.

The government-in-exile has appealed for protests - also reported in other Indian cities - to be 'non-violent' and not embarrass India.

'It's very important not to embarrass the host (India), which means we have asked Tibetans to keep their protest peaceful,' its spokesman Thubten Samphel said.

Seventy Indian sports figures, entertainers and others are taking part in the torch run, including Bollywood actors Aamir Khan and Saif Ali Khan, tennis player Leander Paes and officials from China's embassy in New Delhi.

They will be guarded by about 16,000 police and paramilitary forces as well as an elite anti-terror unit.

Barricades and iron sheeting have been thrown up around the route, traffic has been diverted, trains halted and government offices will be closed during the run, effectively paralysing the city centre.

The Indian Olympic Association has said members of the public were welcome to watch the run, but they will have to negotiate several layers of police and soldiers first.

India has been home to the Dalai Lama since he fled Tibet after a failed 1959 uprising against Chinese rule in his homeland.