India was on high alert yesterday as it celebrated 59 years of independence amid threats of terrorist attacks the prime minister said undermined a two-and-a-half year peace process with Pakistan.

Intelligence reports indicated Islamic militant groups might be plotting major attacks.

Last week, the US Embassy warned groups linked to al Qaida could target hotels, airports or historic monuments in New Delhi, Mumbai or other cities.

In his Independence Day address, Prime Minister Manmohan Singh said terrorists want to derail India's booming economy, disunite its people and spark religious strife.

Singh said every Indian wants to live in a prosperous South Asia where people trade freely, but such aspirations can only be realised in "an atmosphere of peace".

He said India launched initiatives to achieve peace, especially with Pakistan, but terror attacks such as the deadly Mumbai train bombings of July 11 were undoing efforts.

India suspects Pakistan-based Islamic militants were responsible for the blasts, which killed 207.

In January 2004, India and Pakistan agreed to start a peace process aimed at ending their decades-old rivalry and dispute over Kashmir, the divided Himalayan region claimed by both.

Pakistan agreed to crack down on militants who allegedly cross into India's part of Kashmir and stage attacks.