Intelligence agencies have informed police that three trucks loaded with explosives had entered the federal capital, while one of them targetted the Marriot on Saturday leaving a trail of death and destruction with over 50 fatalities.
The whereabouts of the other two are not known, sources were quoted as saying by the Daily Times newspaper.
The hunt for the explosive laden vehicles comes as the interior ministry issued warnings that banned militants groups could carry out strikes in Pakistan's other major cities like Karachi.
The sources said the trucks are still present in the city and the risk of attacks from them had forced police to put security on high alert. Police have also increased deployment of personnel near important buildings, erected pickets on key roads and begun intensive patrolling across Islamabad.
Cars were thoroughly checked by policemen at check posts erected on busy roads across Islamabad since Tuesday night. Vehicles, especially trucks, are being searched by the police at pickets. Police are also keeping a close watch on hotels and guest houses.
Simultaneously, additional home secretary for law enforcement, Shafqat Abbasi has written a letter to Sindh's inspector general of police, Sultan Salahuddin Babar Khattak and ordered him to ensure foolproof security measures for foreigners, especially Chinese nationals and their installations.
"We have ordered the Sindh IG to provide foolproof security to all foreign nationals and sensitive government and foreign installations," Abbasi said.
