"The government has always taken a forthright and genuine stance in condemning the drone attacks. We condemn these acts from the core of our heart," the Associated Press of Pakistan (APP) quoted Sharif as saying.
The prime minister said the government never took a casual stance on the issue of drone strikes and always termed these as acts violating the country's sovereignty and integrity. Sharif said all stakeholders must remain united on the issues of national security and should refrain from misguiding the nation about the government's sincerity.
Sharif: We condemn these acts from the core of our heart
At least six people were killed on Thursday when US drones fired missiles at a seminary in Pakistan's northwest Hangu district.
Iftikhar Ahmad, district police officer of Hangu, said a religious school, Madrassa Dar-ul-Uloom, was targeted by the US drones, and those killed include four students and two Islamic scholars who were believed to be associated with the Haqqani network.
He said that the killed scholars included Mufti Hameed Ullah and Mufti Ahmad Jan who had very good relations with the Haqqani network.
Thursday's attack came a day after Sartaj Aziz, Sharif's advisor on foreign affairs and national security, said in a briefing to a senate committee that the US had assured Pakistan that it would not launch any drone strikes during the peace-talks between the Pakistan government and the Taliban.