"The presence of several foreign and indigenous terrorist groups poses a potential danger to U.S. citizens throughout Pakistan," the warning read. "Across the country, terrorist attacks frequently occur against civilian, government, and foreign targets."
Bilateral ties were strained following a unilateral decision by the U.S. military to target al-Qaida leader Osama bin Laden. He was killed by U.S. forces in 2011 at his Pakistani compound.
The State Department advisory said terrorists in Pakistan use kidnapping for ransom as a common tactic. Protests, meanwhile, may turn violent without warning.
"Threat reporting indicates terrorist groups continue to seek opportunities to attack locations where U.S. citizens and Westerners are known to congregate or visit," the warning said.
Pakistan holds parliamentary elections May 11. Former Pakistani President Pervez Musharraf returned to Pakistan from self-imposed exile to run against former Prime Minister Nawiz Sharif, whom he toppled in a 1999 coup.
Musharraf faces three charges in connection to the 2007 assassination of former Prime Minister Benazir Bhutto, who was campaigning against him at the time.