US drone strikes targeting three militant compounds on Friday killed at least 15 people in Pakistan's restive tribal region near the Afghan border, security officials said.
The strikes in Tundar village in North Waziristan, known as a bastion of Taliban and Al-Qaeda, came a day after Pakistan summoned a US diplomat to protest over drone attacks, calling them 'unlawful'.
Missile attacks from unmanned US aircraft in North Waziristan have now killed at least 30 people since the start of the Muslim festival of Eid on Saturday.
Pakistan has repeatedly criticised American drone attacks in its territory, calling them counter-productive, and a foreign ministry spokesman condemned the latest incident.
A senior security official in the northwestern city of Peshawar speaking on condition of anonymity said US drones fired a total of six missiles, two each on three separate compounds.
"The death from three US drone attacks in North Waziristan has gone up to at least 15," the official told AFP, revising the earlier death toll of eight.
Another security official confirmed the higher figure and said it may rise further as more details of the attack emerged.
Officials said the area targeted is used by militants belonging to Tehreek-e-Taliban Pakistan (TTP), Afghan Taliban allied with Haqqani network and Hafiz Gul Bahadur group.
A third security official confirmed the strikes and said the identities of the dead were not immediately clear.
"We are gradually getting information from the area of the new strikes, which is mountainous and covered by thick forest," he said.
Islamabad and Washington have been seeking to patch up their fractious relationship in recent months after a series of crises in 2011 saw ties between the 'war on terror' allies plunge.
But attacks by unmanned US aircraft remain contentious - they are deeply unpopular in Pakistan, which says they violate its sovereignty and fan anti-US sentiment, but American officials are said to believe they are too important to give up.
Washington considers Pakistan's semi-autonomous northwestern tribal belt as the main hub of Taliban and Al-Qaeda militants plotting attacks on the West and in Afghanistan.
Foreign ministry spokesman Moazzam Ahmad Khan criticised Friday's strikes during his weekly press briefing in Islamabad.
"We regard these strikes as illegal and unproductive," he said.
"These attacks also violate our sovereignty, territorial integrity and are in contravention of international laws."
The surge in drone attacks this week has come after reports of a thaw in Islamabad's difficult ties with the United States following a visit to Washington by Pakistan's spymaster, Lieutenant General Zaheer ul-Islam, earlier this month.
Islam's talks with his CIA counterpart were said to have focused on drone strikes.
Khan said Pakistan was working with the US leadership on the drone issue.
"We are working on various proposals and hope to come up to a mutually acceptable solution," he said.
But he refused to discuss the nature of proposals, saying it was difficult for him to share these with the media.