The militants who brought death and chaos to Mumbai had received months of commando training in Pakistan before launching their attacks, a revelation that will further heighten tension between the two countries.

Indian investigators said yesterday that during interrogation, Azam Amir Kasav, the sole militant taken alive, had revealed that his team had taken "their command in Pakistan". A group of up to two dozen had undergone a year of training overseen by the Lashkar-e-Toiba militant group and conducted by a former member of the Pakistan army. When the training finished, 10 were chosen for the mission.

"They underwent training in several phases, which included training in handling weapons, bomb-making, survival strategies, survival in a marine environment and even dietary habits," a senior police officer said.

The details of the involvement of Pakistan-based militants in last week's brazen attacks that left more than 180 dead came as the US Secretary of State, Condoleezza Rice, called for Pakistan to show "transparency" and to help in the investigations.

Ms Rice, who is cutting short a European visit and is due to arrive in India for talks tomorrow, said: "I don't want to jump to any conclusions myself on this, but I do think that this is a time for complete, absolute, total transparency and co-operation and that is what we expect [from Pakistan]," she said after talks in London with the Foreign Secretary, David Miliband. "What we are emphasising to the Pakistani government is the need to follow the evidence wherever it leads and to do that in the most committed and firmest possible way."

Kasav, a clean-shaven 21-year-old said to be fluent in English, was captured in an iconic photograph during the attacks wearing a black T-shirt with Versace logo. He reportedly told investigators that the militants' training was carried out in two camps, one near Mansehra in Pakistan's north-west and the other near Muzaffarabad in Pakistan-administered Kashmir.

The first training phase involved three months of exhausting physical preparation, including regular 10-mile (16km) runs. Next they received marine training and practised swimming, diving and seamanship. Indian media reported that weapons training followed before the chosen men were sent to Mumbai on a reconnaissance mission, during which they visited the Taj Mahal and Trident-Oberoi hotels.

One report suggested that more militants may be at large after officials searching a fishing vessel that the gunmen had seized to reach Mumbai discovered that there were enough life-jackets and equipment on board for 15 men. Police had initially believed up to 24 militants may have been involved in the operation, but this may have been based on speculation.

In Islamabad, officials said they had not received any evidence from India that a Pakistan-based group had been involved in the attacks. The President, Asif Ali Zardari, again appealed for restraint but also appeared to accept the possibility that Pakistani militants were involved. "Such a tragic incident must bring opportunity rather than the defeat of a nation. We don't think the world's great nations can be held hostage by non-state actors," he said.

"Even if the militants are linked to Lashkar-e-Toiba, who do you think we are fighting?"

Pakistan's Prime Minister, Yousuf Raza Gilani, will today host a meeting of all political party leaders to discuss how to respond to the attacks. He said Pakistan would take action against the "miscreants if there is any evidence against a Pakistani national". However, he also urged India to stop making accusations through the media.

Chaudhry Nisar Ahmed Khan, an opposition politician in Islamabad, has called for Pakistan to be firm with India and insisted that it provide evidence of the involvement of Pakistanis. He said India must "put up or shut up".

On the weekend, India and Pakistan engaged in a display of sabre-rattling. India said it was increasing its security to a "war level". Pakistan responded by threatening to move up to 100,000 troops from its northern tribal areas to its eastern border with India.

Few observers believe relations will plunge to their 2002 level, when the two nations faced off, but there is little doubt that the fallout from the attacks will hamper what had been a gradually progressing peace process.

Meanwhile, a Muslim graveyard in Mumbai has rejected the bodies of the nine attackers. "People who committed this heinous crime cannot be called Muslim," said Hanif Nalkhande, of the Jama Masjid Trust which runs the Badakabrastan graveyard. "Islam does not permit this sort of barbaric crime."