An armed attack on the Sri Lanka team coach in Lahore in 2009 saw seven team members among the injured, while six policemen and two civilians were killed.
Most of Pakistan's home matches for the past decade have been held in the United Arab Emirates, due to security concerns, but Sri Lanka have agreed to visit on tour, having until now played just one T20 match in the country since the deadly attack.
Three ODIs are scheduled to take place in Karachi on September 27, 29 and October 3, before a series of Twenty20s in Lahore.
Several high-profile players - including captains Dimuth Karunaratne and Lasith Malinga - have refused to travel with the 15-man squad, with Sri Lanka naming Lahiru Thirimanne and Dasun Shanaka as skippers for the tour.
— Sri Lanka Cricket (@OfficialSLC) September 11, 2019
The tour may now be in jeopardy, with Sri Lanka Cricket (SLC) having been informed by the office of Prime Minister Ranil Wickremesinghe there is a "possible terrorist threat" to the team.
The national governing body said it had "sought the assistance of the Sri Lankan government to conduct a 'reassessment' of the security situation in Pakistan".
"The decision was taken following a warning SLC received from the Prime Minister's office," Sri Lanka Cricket said.
"Accordingly, the warning highlights that the Prime Minister's office has received reliable information of a possible terrorist threat on the Sri Lankan team while touring Pakistan."
Photo Getty Images. Caption: Sri Lanka's tour of Pakistan appears to be in doubt