Police have questioned four people on Wednesday in connection with a series of bombings which tore through crowded markets in the Indian tourist city of Jaipur, killing at least 80 people and leaving about 200 injured.

"We have picked them up for questioning in regards to the attacks last night but we have not booked them on any charge," a police spokesman said in Jaipur, the site of the bombings late on Tuesday.

Among those being questioned was one of the injured and a city rickshaw puller, the spokesman said, asking not to be named.

A federal team of explosives experts meanwhile arrived in this tourist city from New Delhi to help with investigations into the blast.

Police said seven blasts occurred within minutes of each other during the evening in crowded markets of historic Jaipur, about 260 kilometres (160 miles) from New Delhi.

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

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

Junior home minister Shriprakash Jaiswal said "the people responsible for these attacks have foreign connections," but he refused to point a finger directly at traditional foe Pakistan.

Television pictures showed shopping bags, bloodied sandals and shoes strewn around popular Johri bazaar where one of the bombs exploded.

Pools of blood stained the street outside Hanuman temple, dedicated to the Hindu monkey god. A 10-year-old boy was seen among the dead, and a bride in a red saree still wearing marriage bangles, the Press Trust of India said.

Hanuman Swami, a 22-year-old father of one, was praying outside the temple when he was suddenly hit by flying metal and other debris.

"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, said he 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.

Home minister Kataria said the bombs were either planted on bicycles, rickshaws or in cars, the Press Trust of India (PTI) said.

Prime Minister Manmohan Singh condemned the blasts and appealed for calm, as the government issued a nationwide security alert. The Rajasthan government announced a day of mourning, the PTI agency said.

State borders were sealed and a high alert sounded in the state and neighbouring areas, police said.

The bombings took place as India marked the 10th anniversary of nuclear tests conducted on May 13 in Rajasthan, but it was unclear if there was a link.

India has been plagued by bombings across the country in recent years and 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 an India-Pakistan peace process and damage the country's booming economy.