Authorities boosted security at Islamabad's international airport Thursday after a telephone threat warned a suicide bomber would attack the facility.
Flights were not affected and more than an hour after the time the caller said the strike would take place, no such attack had happened, said senior airport security officer Col. Ashraf Faiz.
"It was a specific threat," he told reporters. "The airport is on red alert."
Pakistan has been on edge since a massive truck bomb devastated the Marriott Hotel in Islamabad on Saturday, killing 53 people and wounding scores more.
On Wednesday, the little-known militant group that claimed responsibility for the Marriott bombing threatened more attacks and warned that Pakistanis should stop cooperating with the United States.
The bombing and the new threats underscored the danger Islamist militants pose to Pakistan, where al-Qaida and Taliban fighters have established bases in tribal regions along the border with Afghanistan.
'Hearts and minds'
The U.S. has pushed Pakistan to crack down on the northwest bases, even launching its own attacks, but those American strikes have outraged a population already unhappy with Pakistan's alliance with the United States.
Pakistani President Asif Ali Zardari told reporters Wednesday on the sidelines of the U.N. General Assembly in New York that international support for Pakistani anti-terror efforts was important, but that unilateral U.S. strikes undermined efforts to win "hearts and minds."
"There is the physical (security) dimension, there is the economic side," Zardari said, according to the state-run Associated Press of Pakistan. "The idea is to increase acceptance of the fight inside Pakistan and outside Pakistan, and we are striving to improve on this idea."
Concerned about the possibility of further attacks, the U.S. State Department has announced it is prohibiting all American government personnel from staying at or even visiting major hotels in Islamabad and the key cities of Karachi and Peshawar, and told them to stay away from restaurants as well.
In addition, a notice from the U.S. Embassy in Islamabad urged American citizens working or visiting there to take similar precautions, while announcing that visa and other routine consular services were temporarily suspended as of Thursday. Emergency assistance to U.S. citizens will continue to be available.
Wednesday's threat of more attacks came from a group calling itself "Fedayeen al-Islam" or "Islam commandos." It called on Pakistan to stop cooperating with the United States and referred to the owner of the Marriott in Islamabad by name.
"All those who will facilitate Americans and NATO crusaders like (owner Sadruddin) Haswani, they will keep on receiving the blows," said the message in English.
It was impossible to verify the identity of the group or say whether it was in a position to make good on the threat. Pakistani officials were not immediately available for comment.
The U.S. has stepped up attacks on suspected militants in the frontier area, mostly by missiles fired from unmanned drones operating from Afghanistan. The incursions — especially a ground raid into South Waziristan by American commandos Sept. 3 — have angered many Pakistanis.
Also Thursday, army spokesman Maj. Murad Khan said seven soldiers and 25 militants died in fighting in the Bajur tribal region the previous day. Hundreds have died in the region in recent weeks in a military offensive against insurgents.