New Delhi said on Sunday it was raising security to a "war level" and had no doubt of a Pakistani link to the attacks, which unleashed anger at home over intelligence failures and the delayed response to the violence that paralysed the country's financial capital.

Officials in Islamabad have warned any escalation would force it to divert troops to the Indian border and away from a US-led anti-militant campaign on the Afghan frontier.

Zardari has vowed to crack down if given proof.

But security officials in Islamabad said Pakistan would move troops from its western border with Afghanistan, where forces are battling al Qaeda and Taliban fighters as part of the US-led campaign against militancy, to the Indian border if tension escalated.

Prime Minister Manmohan Singh said on Sunday he would boost and overhaul the nation's counter-terrorism capabilities, an announcement which came after Home Minister Shivraj Patil resigned over the attacks.