CIA contractor Raymond Davis who killed two Pakistanis in Lahore have revealed in his book that American intelligence network was spread in Pakistan.
Raymond Davis quotes an incident in which DG ISI Shuja Pasha visited CIA Station Chief in Islamabad and asked him that CIA is involved in secret missions inside Pakistan. To this CIA station Chief Homer Barkin responded that I cannot answer your question, you should know that we are involved in all sorts of missions and activities just like you do.
This is not the first time that any US official has disclosed about such activities. John Kerry in his last briefing before he left office talked about special operations centers in Pakistan. His speech created uproar in Pakistan because Pakistani government and other departments always denied such activities.
Wiki leaks also confirmed these reports after it was revealed that Pakistan’s ambassador to USA Husain Haqqani was issuing Visa to Americans without consultation or clearance from other departments.