THE mega cities of Mumbai and Delhi are on high terrorist alert after about 80 people were killed by a serial-bomb attack in Jaipur, one of the India's main tourist destinations.

Eight blasts were detonated within 12 minutes in the crowded laneways of the historic walled city of Jaipur on Tuesday, raising fears of a fresh wave of terrorist attacks in India. At least three children were among the dead and more than 200 people were injured. There were no reports of foreign casualties.

"We are in for a more violent phase of terrorism," one senior intelligence official told the Hindustan Times.

It was the first terrorist attack in Jaipur, the capital city of Rajasthan, which attracts many foreign tourists because of its architectural heritage. One of the bombs was detonated near the 18th-century Hawa Mahal, or Palace of the Wind, and another targeted the famed Johri Bazaar, crammed with jewellers. The death toll would have been higher had not three more bombs been defused.

Rajasthan's director-general of police, A.S.Gill, said bombs had been planted in plastic bags and attached to nine new bicycles. These were then placed with the aim of causing "maximum damage". Bicycles have been used in at least two other terrorist attacks India during the past two years.

There were no claims of responsibility, but authorities were quick to declare the "meticulously planned" attacks the work of terrorists. A junior minister for home affairs in the Indian Government, Sriprakash Jaiswal, said he suspected a "foreign hand" was involved - normally a reference to arch rival Pakistan.

However, the Pakistani Prime Minister, Syed Yousuf Raza Gilani, condemned the blasts.

Three groups - the Bangladesh Harkat-ul-Jihad-al-Islami (HuJI), the Students' Islamic Movement of India (SIMI) and Lashkar-e-Toiba - top the list of suspects.

Jaipur police have detained a dozen people for questioning in relation to the attacks. They have identified where the bicycles used in the attacks were bought and have a description of the buyer.

The attackers appeared to target Hindus, with two of the bombs placed near temples dedicated to the Hindu deity Hanuman. They were also timed to coincide with the weekly gathering of Hanuman devotees. The blasts also coincided with the 10th anniversary of India's nuclear bomb tests which took place at Pokhran, also in Rajasthan.

Jaipur is the base for the Indian Premier League cricket team the Rajasthan Royals, which includes Australian stars Shane Warne and Shane Watson. The team was not in the city at the time of the attacks.

India's last big bomb attack was in the central city of Hyderabad in August when two explosions in a restaurant killed 42 people.