No group has claimed responsibility for Monday's attacks

The Indian Deputy Prime Minister, Lal Krishna Advani, said that Pakistan's condemnation of the attack was a "mere formality", unless Islamabad handed over 19 people wanted by Delhi.

However a Pakistan Foreign Ministry spokesman said it was no time for pointing fingers and making political capital, and re-iterated that there were no such suspects on Pakistani territory.

No group has claimed responsibility for Monday's attacks but Indian officials and politicians say a banned Islamic students group may have been involved, along with a Pakistan-backed Kashmiri militant group.

Citizens of Bombay give their reaction to Monday's deadly bombing In pictures

Security has been stepped up in India following the attacks which left about 150 people injured in the heart of the country's commercial capital.

Police have been put on alert at airports, railway stations and religious buildings as investigations get under way into the blasts at the city's famous Gateway of India monument and near a temple.

But life in Bombay is fast returning to normal after the attacks, with offices and schools open and typically congested traffic across the city, the BBC's Sanjeev Srivastava says.

And on Tuesday, the stock markets bounced back sharply after going down nearly 3% the previous day.

'Tourists sought'

The attacks have been condemned by leaders around the world, including Pakistan, whose government deplored the "wanton targeting of civilians".

But Mr Advani said the Pakistani statement would only be considered "honest" if it was accompanied by the handing over the 19 bombing suspects wanted after an attack on the Indian parliament in December 2001.

In response, Pakistan Foreign Ministry spokesman Masood Khan told the BBC: "We have not given shelter to any Indian nationals.

STUDENTS ISLAMIC MOVEMENT OF INDIA (SIMI) Formed in Uttar Pradesh in 1977 Declared jihad (holy war) against India and aims to convert it to Islam Banned after 11 September attacks, its offices closed and assets seized Simi president Shahid Badar charged under Prevention of Terrorism Act. In jail awaiting trial Has 400 full-time cadres and 20,000 members under 30 Source: Institute for Conflict Management

"This is no time for finger-pointing, nor should Indian leaders try to make political mileage out of this gruesome tragedy. Leaders should avoid issuing negative statements because they are unhelpful."

There have now been six bomb blasts in Bombay, which is also known as Mumbai, in as many months and the reaction is shock, the BBC's Frances Harrison reports from the city.

Our correspondent says small groups of people have been coming to the bomb sites to pay homage to the dead.

Reports say the police are now searching for a family of tourists who are thought to have hired one of the taxis which exploded.

Bombay Police Commissioner R S Sharma said he believed that Lashkar-e-Toiba, a Pakistan-based Islamist militant group, was responsible for the two explosions.

He said it was still too early to say much but he believed the same group was involved in the blasts in the city in December 2002 and January and March this year.

"I personally feel the same Lashkar-e-Toiba group is involved in this," he said. "But it is very difficult to say at this stage. We have certain very vital clues, vital clues on which we are working."

'Gujarat link'

Mr Advani had earlier said that the Students Islamic Movement of India (Simi), acting with the support of Lashkar-e-Toiba, was to blame for the string of other recent attacks in Bombay.

BOMBAY BLASTS July 2003: Three killed in bus blast Mar 2003: 11 killed in commuter train Jan 2003: 30 injured in market attack Dec 2002: 23 injured at McDonald's outlet Dec 2002: Two killed in bus blast Mar 1993: More than 250 killed in serial blasts Profile: Lashkar-e-Toiba Eyewitness: City in chaos

"Earlier these blasts were in buses and in almost all cases the organisation involved has been Simi and acting in conjunction with Lashkar e-Toiba," he said.

He told reporters on Tuesday: "The people responsible before appear to be the people responsible now."

Lashkar-e-Toiba is one of the two Pakistani rebel groups that Delhi blames for the December 2001 militant attack on its parliament which left 15 people dead, including five attackers.

Meanwhile, an Indian official has linked the bombings to continuing religious tensions in the state of Gujarat.

Chhagan Bhujpal, deputy chief minister of Maharashtra state, told NDTV television there was "no doubt" the attacks were linked although he provided no evidence for the claim.

About 2,000 people, mainly Muslims, were killed in riots last year in Gujarat, following an incident in which about 60 Hindu pilgrims were burned to death in a train set alight by Muslims.

Eight of the victims of the latest explosions came from Gujarat, and their bodies are due to be returned to the state.