Failure to do so would risk destroying the peace process aimed at resolving the Kashmir dispute, said Mr Singh, in an abrasive attack after a tour of two hospitals. “Pakistan in 2004 had solemnly given an assurance that Pakistani territory will not be used to promote, encourage, train and abet terrorist elements directed against India. That assurance has to be fulfilled before the peace process or other processes can make progress,” he said.

“We are certain that terrorist modules are instigated, inspired and supported by elements across the border,” he added, clearly upset after his talks with several victims who had lost limbs in Tuesday’s rush-hour attacks.

His remarks brought an angry response from Pakistan.

Doubts were being raised yesterday over whether the meeting to be held next week between the two countries’ Foreign Ministers, to review the peace process, would go ahead on schedule. It was thought that it could be deferred.

Mr Singh said that there was no chance of improved relations until Pakistan-based groups such as Lashkar-e-Taiba — the main suspects for masterminding the Bombay bombings — were dealt with.

Admitting that cities such as Bombay harbour homegrown terrorists, Mr Singh argued that without help from across the border “they cannot act with such devastating effect. They clearly want to destroy our growing economic strength, to destroy our unity and provoke communal incidents.”

The Prime Minister did not detail what sort of support he believes the Bombay cell was given but Indian officials have long argued that Pakistan provides technical assistance, training and funding for an array of militant Islamic groups.

Having been on the brink of war in 2002, the countries have recently engaged in talks, making little progress on the most contentious issue, Kashmir.

Pakistan strenuously denies having any links with the Bombay bombers and President Musharraf has offered to help India to investigate the terrorist attack, which he condemned for the loss of “precious lives”.

The Pakistani Foreign Ministry tried to dismiss the idea of a rupture in diplomatic relations, a spokesman saying: “The peace process between Pakistan and India is a separate matter. It is in the interest of both.”

As the huge murder hunt continued, telephone calls made from Bombay to a backstreet hotel in Kathmandu within minutes of the bombings led to the arrest of two Pakistani men alleged to be members of Lashkar-e-Taiba who are said to have helped to organise the attacks. The men, both in their fifties, are understood to have helped to supply the explosives.

The bombers are now believed to have mingled with commuters on packed station platforms as they used their mobile phones to detonate the devices left aboard seven trains.

Experts describe it as a far more elaborate operation than the attacks on rush-hour trains in London and Madrid.

The investigation has covered half a dozen countries, including Afghanistan and Bangladesh as well as Pakistan.

Police in Bombay have named three Indian-born men — again, all allegedly prominent members of Lashkar-e-Taiba — as responsible for recruiting the city’s terrorist cell. They remain at large.

The biggest round-up by the anti-terrorist squad witnessed in the port city continued with further armed raids.

Muslim political leaders said that more than a thousand people were being held.

Abu Asim Azmu, of the Muslim Samajwadi Party, told The Times that he feared a backlash by his community if mass detentions continued.

So far, Hindus and Muslims have been united in condemning the bombers and refrained from the revenge attacks that followed bombings in 1993.

One of the biggest raids targeted a shantytown on the edge of Malwani, north of the city centre. One man, 30, a father of three, said that half a dozen police had burst into his tiny shack, shone a torch in his face and demanded he identify the location of a bomb factory. He was held for 36 hours and released without charge.

More than 25,000 people are squeezed into the slum with no sanitation or running water.

A boy who has been in a coma since the bombings and has head injuries was last night identified by his parents, who have been searching for him for days and brought a photograph to show police and hospital staff in Borivali. He is Rakesh Parihar, 8, from Nerul. His mother said: “I am so happy and relieved to find him.”

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