According to the American media reports, the declassified documents have revealed that the US National Security Agency (NSA) had been spying on Pakistan's former ruling Peoples Party (PPP) in 2010.
Under a 2010 certification approved by the Foreign Intelligence Surveillance Court, NSA was permitted to spy on 193 foreign governments as well as foreign factions, political organizations and other entities, Washington Post reported.
"Pakistan has noted with concern recent media reports indicating that it is among the countries subject to surveillance by US government departments," the Pakistani Foreign Ministry said in a statement.
"The US Embassy in Islamabad was conveyed today that such an action against Pakistani government departments or other organizations, entities and individuals is not in accord with international law and recognized diplomatic conduct," said the statement.
The foreign ministry said the reference to a political party in Pakistan was surprising, adding that "the US side was further conveyed that surveillance was contrary to the spirit of friendly relations between our two countries."
Pakistan urged the US to stop such activities in the interest of friendly and cooperative ties.
A US classified document revealed on Monday shows that US spy agency had been sanctioned to spy on most countries and some international bodies and political parties including the PPP and the India's Bhartiya Janata Party, which rules in India.
The PPP condemned the United States for spying on the party and demanded of the government to raise the issue through diplomatic channels with the US.