Indian police have released sketches of two men said to have jumped off a train heading towards Pakistan minutes before it was struck by two fatal bombs, amid accusations of major security failures.

The images came as the Pakistani foreign minister arrived in Delhi, where he aims to sign a deal on nuclear security as part of peace talks between the two historic Asian rivals.

India and Pakistan have already shown a rare unity in denouncing the attacks, which took place on Sunday night when two bombs placed in suitcases exploded, triggering a fire which raged through two of the carriages on the Samjhauta (Friendship) Express. The vast majority of victims were Muslims from Pakistan.

In sharp contrast to previous attacks, both nations have been careful not to apportion blame, instead moving quickly to insist the bombing would not damage the delicate peace process that began in 2004.

Today’s visit by Khursheed Mehmood Kasuri appeared to confirm that a diplomatic fallout had not occurred, with the Pakistani Foreign Minister even scheduled to visit a hospital in Delhi treating those seriously injured in the blast.

“It is a horrendous act of terrorism which everybody would condemn unreservedly,” Mr Kasuri said, adding that the bombers should not be allowed to achieve their objectives. “In fact, if at all, we should hasten the peace process,” he said.

Police said the two men they want to question boarded the vehicle from its starting point in Delhi, soon after which they began arguing with the conductor, saying they were on the wrong train. They were allowed to jump off when the train slowed down on the approach to Panipat - about 15 minutes to 20 minutes before the crude bombs detonated.

Jeremy Page, correspondent for The Times in Delhi, said it was understood that the description of the two men came from testimony given by one of the survivors of the blast, who remains in intensive care in a hospital in Delhi along with his wife and one-year-old daughter.

The survivor, whose five other children were killed in the attack, is said to have told officers that he saw the two men jumping off after telling the conductor they had accidentally boarded the wrong train.

The train is supposed to head from the capital to Atari, at the Pakistani border, without any stops, and the revelation that two were allowed to get off appeared to highlight what many passengers already say - that security on trains and at the stations is cursory, at best.

In further signs of lax security, police admitted that 13 passengers had travelled across to the Pakistani side of Atari without passports, while newspaper reports claimed that two railway ticket clerks had been suspended for selling tickets without checking passengers’ passports and visas.

“There is no security at all at the station,” said Ati-ur-Rahman, as he waited Monday for word about his missing cousin who was headed for Lahore, the line’s final stop in Pakistan. “There are only a few rude constables and all they’re looking for is a few hundred rupees. They don’t check anything."

Lalu Prasad, the Railway Minister, virtually acknowledged as much hours after the blast, telling reporters yesterday: “Though there are metal detectors, we don’t have the equipment to check what is inside the luggage. We can’t deny that.”

Meanwhile, a drunken Pakistani passenger on the train was today detained for questioning, Indian officials said, although there seemed to be little indication that the man – who is from Karachi - was involved in the attack.

“He was found in a drunken state and he’s being questioned. But his account has been inconsistent and we have no definite conclusions yet,” said Bharti Arora, a senior Haryana state railway police official.

In Panipat, 50 miles from Delhi, relatives continued today to gather at the hospital to give DNA samples in an attempt to identify the bodies.

Less than 20 of the victims had been formally identified by this morning, with most of the corpses mutilated beyond recognition. A small camp has been set up in the town for the Pakistani relatives of the victims, providing food and shelter for them as they waited for news of their loved ones.

Page said that the attack had put the spotlight on the human cost of divisions between India and Pakistan, with the train targeted providing one of the very few means by which families and friends split between the two countries could visit each other.

“On both sides, people’s attention has now been drawn to those families, many of whom were split up after the partition of India and Pakistan and can only visit their relatives across the border very rarely. By highlighting those people’s plight, the attack seems to have had the effect of pulling India and Pakistan together rather than pushing them apart,” he said.

Manmohan Singh, the Indian Prime Minister, has already declared his country’s “abhorrence for this heinous terrorist act.” His comments echoed those made earlier by President Pervez Musharraf of Pakistan, who said: “We will not allow elements which want to sabotage the ongoing peace process to succeed in their nefarious designs. Such wanton acts of terrorism will serve only to further strengthen our resolve to attain the mutually desired objective of sustainable peace between the two countries.”

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