Pakistani police scoured hills surrounding the capital Islamabad and sent additional units to protect key installations on Monday amid tightened security ahead of a major Muslim holiday and after a bomb wounded 14 people on a train.
Police and soldiers go on alert every year in the closing days of the holy Muslim month of Ramadan, which this year coincides with a global security alert issued by the United States which closed more than a dozen embassies in the Middle East and Africa following an al Qaeda threat.
"We have beefed up security in Islamabad, particularly at the Faisal Mosque since there is a security threat," Mohammad Rizwan, a senior police officer, told Reuters.
"We have also combed the Margalla Hills, setting up pickets at certain points."
The mosque is the largest in Pakistan and sits at the foot of the majestic Margalla Hills, the first foothills to the Himalayas.
The bomb exploded on a train travelling between the southern financial hub of Karachi and the ancient city of Lahore, capital of Punjab province. No one was killed.
It was unclear whether police were hunting a specific target or whether the increased security was a reaction to an embarrassing jail break last week in which more than 250 prisoners were freed from jail in a militant attack.
Pakistan's police are notoriously under-equipped, poorly trained and under-funded. Security forces sometimes resort to blanket bans to counter potential threats, for instance by banning motorcycles or shutting down telephone networks.