Islamabad pledges support as New Delhi airport is closed during security scare.
A security scare at New Delhi's international airport on Thursday highlighted jitters after the Mumbai attacks, as Pakistan vowed "strong action" if anyone was shown to be involved from its territory.
The Delhi airport was locked down for about 40 minutes overnight after security guards heard what they thought were gunshots, but the incident was later thought to have been a false alarm.
"There were no eyewitnesses to any gunshots and no rounds were recovered," said Udayan Bannerjee, head of the paramilitary Central Industrial Security Force (CISF) which is responsible for airport security.
"Everything is normal," he said.
Security was tightened across India after last week's attacks on Mumbai, and the alert level at several airports was raised even higher on Thursday after defence minister A.K. Antony warned of possible "terror strikes from the air."
There have been fears of a fresh attack to coincide with the December 6 anniversary of the destruction of the Babri mosque in northern India by Hindu extremists in 1992.
India has said that all 10 attackers involved in last week's Mumbai attacks came from Pakistan and has demanded Islamabad hand over 20 terror suspects.
The gunmen landed in rubber dinghies in Mumbai and wreaked havoc with automatic weapons and hand grenades, in an assault that killed 172 people, including 26 foreign nationals.
US Secretary of State Condoleezza Rice was in Islamabad Thursday in an effort to defuse tension in the region after visiting New Delhi the previous day.
Rice said it was crucial for the Pakistani government to provide full and transparent cooperation with the Indian investigations into the Mumbai bloodshed.
Pakistani president Asif Ali Zardari said he was determined that Pakistan would not be used to orchestrate attacks or shelter terrorists such as those who committed last week's outrage.
"The government will not only assist in investigation but also take strong action against any Pakistani elements found involved in the attack," Zardari said in an official statement issued after he met with Rice.
"Pakistan is determined to ensure that its territory is not used for any act of terrorism," he added.
Pakistan's role in the US-led "war on terror" has come under renewed focus since the devastating assault in Mumbai, in which the attackers laid siege to hotels and other sites in the city for 60 hours.
Suspicion has fallen on Lashkar-e-Taiba, a Pakistan-based militant group which has fought Indian control of divided Kashmir and which attacked the Indian parliament in 2001, nearly pushing the two nations to another war.
Pakistan has been a key US ally since the September 11 attacks seven years ago, but many critics openly question whether elements in the Pakistan military and intelligence services support Islamist militants.
Rice said she had found the Pakistani leadership "very focused and committed" to action.
"Everybody wants to prevent further attacks," she told reporters after talks with Zardari, Pakistani Prime Minister Yousuf Raza Gilani and senior army officials.
Indian Foreign Minister Pranab Mukherjee told Rice on Wednesday that his country was considering all options in responding to the attacks.
The United States is concerned about any military stand-off with India that might see Pakistan move troops from its border with Afghanistan - a crucial area where Taliban and Al-Qaeda fighters have been gaining ground.