NEW YORK - Pakistani investigators have unearthed substantive links between the gunmen who attacked Mumbai in November and a banned militant group, the Wall Street Journal reported Wednesday. The newspaper said that at least one top LeT leader, Zarar Shah, captured in a raid early this month in Pakistan Occupied Kashmir, had confessed to the group's involvement in the attack. "He is singing," an unidentified Pakistani security official told the Journal, referring to Shah. "The disclosure could add new international pressure on Pakistan to accept that the attacks, which left 171 dead in India, originated within its borders and to prosecute or extradite the suspects," the newspaper said in a dispatch from Islamabad. "That raises difficult and potentially destabilising issues for the country's new civilian government, its military and the spy agency, Inter-Services Intelligence - which is conducting interrogations of militants it once cultivated as partners". India's accusation of a Pakistani link to the assault on Mumbai has revived old hostilities between the nuclear-armed rivals and raised fears of conflict. Pakistan has condemned the Mumbai attacks and has denied any state role, blaming 'non-state actors'. Shah's admission was backed up by US intercepts of a telephone call between Shah and one of the attackers during the assault, the Pakistani security official told the newspaper. Shah told interrogators that he was one of the main planners of the assault and he had spoken to the attackers during the rampage to give them advice and keep them focused, the newspaper cited a second person familiar with the investigation as saying. Shah had implicated other LeT members, and had broadly confirmed the account the sole captured gunman told Indian investigators, the second person told the newspaper. According to Indian reports, the captured gunman told Indian interrogators the 10 attackers trained in Pakistan Occupied Kashmir and later went by boat from Karachi to Mumbai. Pakistan has repeatedly said India has not provided evidence. Shah was picked up with another LeT commander, Zaki-ur-Rehman Lakhvi, during Pakistani raids on militants launched in response to the Mumbai attack, Prime Minister Yousaf Raza Gilani told reporters on December 10. Pakistani authorities did not have evidence that the LeT was involved in the attacks before the militants were arrested in Kashmir, the security official told the newspaper. Their arrest was based only on initial guidance from US and British authorities, the newspaper cited the official as saying. Pakistan has promised to prosecute anyone if sufficient evidence is found linking them to the Mumbai attacks but it has ruled out sending any Pakistanis to India for trial. The probe, the Journal said, also is stress-testing an uncomfortable shift under way at Pakistan's spy agency - and the government - since the election of civilian leadership replacing the military-led regime earlier this year. Military and intelligence officials, it says, acknowledge they have long seen India as their primary enemy and extremists such as Lashkar as allies. But now the ISI is in the midst of being revamped, and its ranks purged of those seen as too soft on militants. That revamp and the Mumbai attacks are in turn putting pressure on the civilian leadership, which risks a backlash among the population if it is too accommodating to India. "The ISI can make or break any regime in Pakistan," retired Gen Mirza Aslam Beg, a former army chief, was quoted as saying. "Don't fight the ISI." The delicate politics of the Mumbai investigation, the Journal said, have given the spy agency renewed sway just when the government was trying to limit its influence. A Western diplomat told the newspaper that the question now is what Pakistan will do with the evidence it is developing. The big fear in the West and India is a repeat of what happened after a 2001 attack on India's parliament, which led to the ban on Lashkar. Top militant leaders were arrested only to be released months later, the Journal noted. Lashkar and other groups continued to operate openly, even though formal ISI links were scaled back or closed, the diplomat was quoted as saying. "They've got the guys. They have the confessions. What do they do now?" the diplomat said. "We need to see that this is more than a show. We want to see the entire infrastructure of terror dismantled. There needs to be real prosecutions this time." A spokesman for Pakistani President Asif Ali Zardari, Farhatullah Babar, was quoted as saying that he wasn't aware of the Pakistani investigation yet producing any links between Lashkar militants and the Mumbai attacks. "The Interior Ministry has already stated that the government of Pakistan has not been furnished with any evidence," he said. The Pakistani security official, it said, cautioned that the investigation is still in early stages and a 'more full picture' could emerge once India decides to share more information. Agencies add: Vishnu Prakash, a spokesman for India's Foreign Ministry, said in a telephone interview that all India's evidence will be shared with Pakistan soon, when the investigation is complete. But Prakash expressed doubt Pakistan would act, based on what he said was its investigative track record: "Whenever actionable intelligence is given, our friends make sure it is neutralised, and then it cannot be acted upon," he said. "Traditionally there has been a sort of disconnect between the political leadership and the leadership of the security establishment," said Babar, the spokesman for Zardari. Under the new regime, he said, "There is harmony." There also have been increasing tensions. Zardari has faced frequent reminders that the military's step back from political control has its limits, and could be reversed. Zardari initially offered to send Gen Pasha himself to aid India's investigation into the Mumbai attacks, then had to rescind it when the military objected. He surprised the military this month by announcing Pakistan would never hit India with a first-strike nuclear attack. Two months before his election, Zardari as party chief mounted an attempt to wrest the control of the ISI from the military and place it under a close political adviser. Word spread through a wedding attended by Pakistan's top army brass. "I was certainly not consulted," Gen Kayani told another guest. Top army officials started working the phones. The next day, July 27, the government announced that its original notice had been 'misinterpreted'. It later withdrew the notice entirely.