Pakistan is reported to have put its forces on high alert after someone pretending to be India's foreign minister made a phone call to President Asif Ali Zardari threatening war after the Mumbai attacks began.
Dawn newspaper said on Saturday that the caller on 28 November threatened military action unless Pakistan acted immediately against the perpetrators of the killings in Mumbai, which began two days earlier.
The paper says Pakistan's air force was on the "highest alert" for the next 24 hours.
India blamed Islamists based in Pakistan for the attacks in its financial capital, which killed 171 people.
The newspaper said the episode triggered intense international diplomacy, with some world leaders fearing India and Pakistan could slip into an accidental war.
Dawn also reported the caller, posing as Indian Foreign Minister Pranab Mukherjee, tried to telephone US Secretary of State Condoleezza Rice, but the call was not put through to her due to specific checks by US
officials.
It took frantic phone calls between Washington, Islamabad and New Delhi to cool the temperature.
According to Dawn, Dr Rice called Mukherjee in the middle of the night to ask why he had adopted such a a threatening tone, but he assured her that he had not spoken to Zardari.
Calm was restored by the evening of 29 November.
Pakistan and India went to the brink of war in 2002 following an attack on the Indian parliament in December 2001.
Both states have been nuclear-armed since 1998.
Dawn said President Zardari's staff had bypassed usual verification checks for a call for the president, but the government said he received the call after it was properly verified that it originated from India's Ministry of External Affairs.
The newspaper said Indian officials had denied to US counterparts that the call came from its ministry and said the number could have been manipulated.
Indian and US officials suspect the Lashkar-e-Taiba group was behind the Mumbai attack. The organisation has had ties with Pakistani intelligence in the past.
