Islamabad - Nuclear-armed Pakistan edged to the brink of war with India when its president received a threatening call from someone posing as Indian Foreign Minister Pranab Mukherjee following last week's Mumbai attacks, a media report said Saturday.

The caller, who was put through to President Asif Ali Zardari late in the day on November 28 without verification of his claimed identity, warned that India would take "military action if Islamabad failed to immediately act against the supposed perpetrators of the Mumbai killings."

According to the Dawn newspaper, as the phone call ended many in the president's office were convinced that the "Indians had started beating the war drums." Intense diplomatic and military activity started in Islamabad, the report said further.

Pakistan's air force was put on highest alert and jet fighters patrolled over and around the federal capital with live ammunition, while messages were sent to top officials in Washington, including US Secretary of State Condoleezza Rice, about the gravity of the situation.

But Mukherjee denied that he had made any phone call to Zardari when Rice contacted him in the middle of night on Friday. With international efforts, the situation was defused by late Saturday.

But "for nearly 24 hours over the weekend the incident continued to send jitters across the world. To some world leaders the probability of an accidental war appeared very high," the newspaper reported, citing several unnamed Pakistani political, diplomatic and security sources.

Investigations are underway to establish the identity of the caller. Pakistani authorities suspect the phone call came from a number in New Delhi and might have been someone in India's foreign ministry, a claim the Indians rejected outright.

Tensions between India and Pakistan escalated after last week's terrorist attacks in Mumbai that left more than 170 people dead and over 300 injured.

The Indian police claim the 10 attackers were linked with Pakistan-based Islamic militant outfit Lashkar-e-Taiba, which is fighting a guerrilla war in Indian-administered part of Kashmir.

The nuclear-armed South Asian neighbours both claim the region area and have fought three wars during the 61 years of their existence over the conflict.

Early this week, Rice visited both New Delhi and Islamabad and called upon Pakistan to help in the Mumbai investigations and punish the culprits behind it. At the same time, she urged India to show restraint. (dpa)