Millions are expected at the celebrations

The Indian Prime Minister, Atal Behari Vajpayee inaugurated the celebrations and paid tribute to the "great sacrifices" made by Sikhs over the centuries."

"The birth of the Sikh religion gave India a new lease of life and helped forge unity among Indians because it is casteless," he said.

The prime minister then joined the pilgrims to pray at the town's main shrine, the Takht Kesgarh.

Three million expected

Anandpur Saheb, which lies in the shadow of the Himalayan foothills is usually a sleepy town of about 10,000 people, but the organisers of these celebrations say up to three million pilgrims are expected over the next seven days.

Sikh holy men from Pakistan enter India

India and Pakistan have agreed to help Sikh pilgrims wanting to cross their borders to attend various religious festivals.

A BBC correspondent in Islamabad says the move is one of the latest in efforts by both countries to improve relations between them.

Officials say it will be the first time in more than 50 years that Pakistani Sikhs will travel to the Indian state of Punjab for the festival at Anandpur Saheb.

Hopes for spiritual revival

Anandpur Saheb is home to Sikhism's second holiest shrine, after the Golden Temple in Amritsar.

The Golden Temple in Amritsar

The head priest of the Golden Temple told the BBC that she hopes the festivities will also rekindle interest in the faith among young Sikhs.

Sikhism itself was actually founded about 500 years ago, but its tenth guru, Gobind Singh, changed the face of the religion in 1699 by giving it a martial aspect, requiring Sikhs to leave their hair uncut and to carry a symbolic sword.

Sikh elders are worried about the increase in tendency among the young, especially abroad in Europe or America, to cut their hair or ignore other demands of Sikhism.