Islamabad: Pakistan`s foreign ministry Tuesday summoned US Charge d`Affaires Richard Hoagland to lodge a formal protest over the series of drone strikes in the country, the ministry said.
The protest came a day after two US drones killed at least 16 people in North Waziristan Monday, the third strike in the area over the past three days.
At least 151 people have been killed in 20 drone strikes launched this year.
"US Charge d`Affaires Ambassador Richard Hoagland was called to the ministry of foreign affairs today (Tuesday). He was officially conveyed the government`s serious concern regarding drone strikes in Pakistani territory," Xinhua quoted a ministry statement as saying.
"He (Hoagland) was informed that the drone strikes were unlawful, against international law and a violation of Pakistan`s sovereignty," the ministry said.
The statement recalled that the Pakistani parliament had in April stated that the drone strikes were unacceptable.
"Drone strikes represented a clear red-line for Pakistan," the US diplomat was told.
Anti-US sentiment runs high in Pakistan, basically stemming from the drone strikes in Pakistan`s northwest border region. The drone strikes have killed hundreds of civilians.
Pakistani authorities have repeatedly condemned the drone strikes in the past but the US has never stopped the attacks.