Reporting from Islamabad, Pakistan, and New Delhi — A hoax caller claiming to be India’s foreign minister spoke to Pakistan’s president in a “threatening” manner during the final hours of the Mumbai attacks, prompting Pakistan to put its air force on its highest alert for nearly 24 hours, a Pakistani news report said today.

Meanwhile, authorities in India reported the first arrests since the end of the siege in Mumbai, which killed more than 170 people. Two men in the eastern city of Kolkata, formerly Calcutta, were detained by police and accused of providing the mobile phone cards used by the attackers.

The hoax call and subsequent air force alert reported by the English-language Dawn newspaper underscored the volatile atmosphere between the nuclear-armed neighbors during the 60-hour rampage by gunmen in India’s commercial capital that began the night of Nov. 26.

The report also seemed certain to raise new questions about the competence of Pakistan’s civilian government, elected less than a year ago. The civilian leadership has already been criticized for initially promising to send the chief of its main spy agency to help in the Indian probe, then hastily reneging after objections from the political opposition and the security establishment.

The newspaper’s account said it took intercession by U.S. Secretary of State Condoleezza Rice and other diplomats to establish that the Indian foreign minister, Pranab Mukherjee, had not made the call to President Asif Ali Zardari on the night of Nov. 28.

A U.S. Embassy spokesman, Lou Fintor, said he was unaware of any such incident having occurred, and a Pakistan Foreign Ministry spokesman, Mohammad Sadiq, referred calls to the Information Ministry, which said it would be making a statement later on what it described as the “so-called” hoax.

However, a Western diplomat and a Pakistani security official confirmed the broad outlines of the Dawn account.

India has blamed Pakistan-based militants in the attacks but not the Pakistani state. Pakistan has denied any official involvement, and there is widespread public anger over the fact that India accused Pakistani elements even while the attacks were still unfolding.

During the air force alert, Pakistani warplanes carried out patrols while carrying live weapons, Dawn said. Senior intelligence officials also suggested to reporters during that interval that Pakistan might shift tens of thousands of troops from the border with Afghanistan to the Indian frontier.

The incident reportedly began when a caller who identified himself as Mukherjee urgently requested to speak with Zardari. The two had earlier been in phone contact, and because the situation was so fluid at that point, presidential aides bypassed normal identification checks and put the call through, the newspaper’s account said.

Most analysts believe a Pakistani group could not have carried out the Mumbai attacks without the help of local Indian accomplices, and the two arrests reported today by authorities could help support that thesis.

However, a police official in West Bengal, the state where Kolkata is situated, cautioned that the two men did not necessarily have direct links with the attackers or prior knowledge of the plot.

Authorities said the arrested pair had bought large batches of cellphone SIM cards that included one later used by the gunmen during the attacks. How the SIM cards came into the attackers’ possession remained unclear.

Police say the gunmen were in touch by mobile phone with handlers in Pakistan while the siege was taking place, allegedly seeking guidance on how to proceed and on whom to kill and whom to spare among their hostages at luxury hotels and other sites.

Police have already released details of another Indian national who they say was recruited by the Pakistani militant group Lashkar-e-Taiba to scout out possible target sites in Mumbai, including some of those that were hit during the recent attacks. Police say the man was found carrying hand-drawn maps of the sites.

Although it has not been established whether the man was directly connected to the attacks that eventually unfolded, public outrage in India has grown over the perceived failure of authorities to act on intelligence pointing to an imminent strike on Mumbai. On Friday, India’s new home minister admitted that there had been “lapses” in security.

Los Angeles Times