Indian police were interrogating a dozen men on Wednesday detained after eight near-simultaneous bombings killed about 80 people in crowded markets in the tourist city of Jaipur.

"We have detained around one dozen people and we are trying our best to unravel the conspiracy behind this dastardly attack," Rajasthan state home minister Gulab Chand Kataria told AFP.

Among those detained in the city, which was under a day-time curfew, were one of the 200 wounded and a rickshaw puller, a police official added, asking not to be named.

A federal team of explosives experts meanwhile arrived from New Delhi to help with inquiries into Tuesday night's blasts.

Eight bombs went off within minutes of each other in crowded markets close to several Hindu temples in what police said was a terror attack on the city which lies 260 kilometres (160 miles) west of the Indian capital.

One unexploded bomb was found attached to a bicycle at one of the explosion sites. It was defused and handed over to the explosives experts, police said.

Schools and government offices shut down Wednesday in a day of mourning across the western desert state of Rajasthan of which Jaipur is capital.

The bombs were planted on bicycles and rickshaws or in cars.

"It's a terror attack. There was no (intelligence) report of this," said police director general A.S. Gill.

No claims of responsibility were reported.

Government officials are usually quick to blame Islamic militants based in Pakistan for such attacks, which have plagued India in recent years.

India's junior home minister Shriprakash Jaiswal told reporters "the people responsible for these attacks have foreign connections," but he refused to point a finger directly at traditional foe Pakistan.

In Jaipur hospital wards and at the morgue, the dead included Hindus and Muslims, a strong minority in the city, an AFP reporter said.

A shock of thick black hair was all that peeped out from under a white sheet that covered a small body at the morgue.

Ten-year-old Kanha Mahar had gone to a temple to the Hindu deity Hanuman on a traditional day to pray to the monkey god.

"We were looking for him all evening," said his uncle Jagdish Kumar Gathera, who found him at the hospital.

Gathera and other relatives looked on in shocked silence as Mahar's body was taken off a rusty gurney, leaving behind a pool of blood.

Hanuman Swami, a 22-year-old father of one, said he was at the Hanuman temple when he was hit by flying metal.

"I was standing outside the temple praying when I heard an explosion and I just fell down," said Swami who was rushed to Sawai Mansingh hospital.

Muhammad Frarid, 29, was heading home from work when the blasts hit.

"I felt like I was hit by lightning and I couldn't really figure out what was happening," the father of five told AFP at the same hospital, a blood-stained bandage around his arm.

Several of the explosions took place along the walled city's Johari bazaar, a strip of shops housed in pink buildings with filigreed windows that are the hallmark of Jaipur, known as the pink city.

"I heard two explosions ... then a bomb went off right in front of me," said Malchand Bagoria, who runs a fruit stall opposite one of the bomb sites.

"Then I saw a woman's body go flying through the air. There were so many bodies."

Prime Minister Manmohan Singh condemned the blasts and appealed for calm, as the government issued a nationwide security alert. State borders were sealed.

World capitals from Washington to Paris and London condemned the attacks.

In New Delhi, US ambassador David Mulford offered US help in the investigations, an Indian official said.

Cities across India have been bombed repeatedly in recent years and New Delhi routinely points the finger at foreign-based Islamic militant groups fighting New Delhi's rule in the Himalayan state of Kashmir.

Analysts say Islamic extremist groups are attempting to stoke sectarian tensions to derail a peace process with Pakistan and damage India's booming economy.

Jaipur is popular with foreign and domestic tourists but there were few in the city in mid-May, the hot season in northern India.