KARACHI, Feb 28: A red alert was sounded at the Karachi airport on Saturday following reports about the presence of Osama bin Laden, chief of the Al Qaeda network, in the boarder area of Wana, South Waziristan.

Well-placed sources said that the crisis control room at the airport had been re-opened immediately and security was beefed up considerably in view of any possible backlash in the aftermath of the Wana operation. The crisis control room had been closed down following the end of Afghanistan war.

A senior official of the Airport Security Force (ASF) said: "We have intensified security at the Karachi airport in view of multiple threats." He, however, did not explain nature of the 'multiple threats'.

He said: "There are three stages of alert - alert, high alert and red alert - and we have imposed a red alert." The security, he added, was intensified at airports on the instructions of the federal government. All passes issued to civilians to enter the airport lounge were suspended immediately. Unnecessary protocols were also abandoned and checking of passengers and their luggage increased.

Police and Rangers were also placed on a high alert.

The police flag-marched different roads in Karachi as a show of strength aimed at assuring people of the safety and security being ensured.

"It was also a message to criminal elements that the police are on alert and ready to foil their evil design, if any", a senior official said.

DIG Operations Tariq Jamil said: "We have already placed the force on a high alert in view of the Muharram processions and religious activities. However, due to the 'multiple threats', we have also provided guards to foreign missions, dignitaries and residences of consul generals."

Besides, he said, security around mosques, Imambargahs, churches, temples, religious seminaries and other worship places had also been intensified.

Police said that security at foreign restaurants and installations had been beefed up. The deployment at public places, government offices and buildings had been increased to meet any untoward incident.

Sources in the law-enforcement agencies said that the decision to intensify security was taken following threats of terrorist attacks on public places, government property, officials, as well as on the US and other foreign interests.

A senior official said that terrorist attack similar to one on June 14 near the US consulate might take place.

Meanwhile, leaves of police personnel have been cancelled and they have been asked to resume their duty at all costs.

Police would also use a helicopter for air-patrolling over the areas declared 'vulnerable' to a possible attack, the sources added.