The Taj Mahal Palace hotel was among the gunmen's targets
India's foreign minister has denied making a phone call that prompted Pakistan to put its forces on alert after the Mumbai attacks.
Pranab Mukherjee said the call was a hoax which Pakistan was using to divert attention from the fact its nationals were involved in the attacks.
Pakistan insists the "threatening" call, to President Asif Ali Zardari, came from India's foreign ministry.
Meanwhile Indian police say the only gunman in custody was a "petty thief".
Rakesh Maria, the chief police investigator, told the Associated Press news agency that the gunman, Azam Amir Qasab, had been indoctrinated by the banned Islamist militant group, Lashkar-e-Taiba.
Islamabad denies any involvement in the attacks which left at least 170 people dead, but some of the gunmen are said to have had links to Pakistani militants.
On Saturday, Pakistan's High Commissioner to London Wajid Shamsul Hassan said Pakistan feared India was planning to launch a military strike at the height of tensions over the Mumbai attacks "to teach Pakistan a lesson".
Mr Hassan said high-level US and British officials intervened to calm the situation.
'Confusing the public'
On Saturday, the Pakistani Dawn newspaper reported that the country had been put on high alert during the crisis after what the paper called a hoax call was made to President Zardari.
A caller claiming to be Mr Mukherjee spoke to the Pakistani leader in a threatening manner on 28 November, Dawn reported.
But Pakistan's Information Minister Sherry Rehman later denied it could have been a hoax.
It is, however, worrying that a neighbouring state might even consider acting on the basis of such a hoax call
Pranab Mukherjee Indian Foreign Minister
The minister said "the call was placed from a verified official Phone Number of the Indian ministry of external affairs".
In a statement released on Sunday, India's foreign minister insisted the call - of which he had been notified by a third country - was a hoax.
"I can only ascribe this series of events to those in Pakistan who wish to divert attention from the fact that a terrorist group, operating from the Pakistani territory, planned and launched a ghastly attack on Mumbai," Mr Mukherjee said.
"It is, however, worrying that a neighbouring state might even consider acting on the basis of such a hoax call, try to give it credibility with other states, and confuse the public by releasing the story in part," he said.
India says the surviving gunman was a Lashkar-e-Taiba militant
Nine of the 10 militants believed to have mounted the attack on 26 November died.
Indian media have named the surviving gunman as Azam Amir Qasab. He is described as a Pakistani, and is reported to have links to a Pakistan-based Kashmiri militant group, Lashkar-e-Taiba. The group denies involvement.
The chief Indian investigator said that Amir Qasab had been a low-level thief, before going to a camp run by Lashkar-e-Taiba.
"The moment he came under their wings, the indoctrination started. And that's when he decided there should be some meaning to his life and jihad was his calling," Rakesh Maria said.
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